Maximum Possible Fuel Economy?

[Slvr99LS]

Would you believe 33mpg out of a 3,900 pound automobile with nearly 300HP? Read on....

Having owned this '99 LS for about a month now and logging somewhere between 600-700 total miles, I've definitely had the time to make some general observations and form a few opinions. Before buying the car, one aspect of concern, particularly with oil surging back towards the $70-buck-a-barrel mark and premium unleaded soaring right through $2.50+ a gallon (just in time for the summer vaca season of course - ever notice how that happens yearly like clockwork? <_< ) was definitely fuel economy. Yes I realize that buyers of premium luxury automobiles aren't supposed to be concerned with such trivial issues as how many dead dinosaurs an all-aluminum V8 consumes for dinner, but perhaps I don't fit the typical ownership mold. Short of jumping on the proverbial bandwagon and buying a Prius (vomit), I'm surely not against helping do my part for the 'Greener Good' of it all. Hey, we're all in this together. That includes maintaining all vehicles under my care to a very high standard of tune which would surely bring a broad smile to an ASE certified technicians face... as well as distributing plenty of hard-earned dollars with various parts vendors, both locally and nationally, more often than I care to mention. Being on a first-name basis with all the employees at Pep Boys and Autozone is nothing to brag about!

Now, regarding fuel economy, since I do keep track of such things, I recall some years ago my previous '92 LS-400 averaging just over 20mpg in mixed driving with an absolute high of 29 on a straight, flat-highway run with cruise set at a leisurely 65 and change with the windows up and no A/C. Might've even been slightly downhill with a sustained tailwind. Good coat of wax too never hurt. Less wind resistance. :D You know, it really did annoy me that I couldn't get that car to break 30mpg. Oh well. Not exactly the end of the world. If minimizing ones carbon footprint is truly paramount, there's always the first-gen Honda Insight... or better yet, a bicycle. Anyhow, based on that experience, I was certainly curious what the '99 model with all of its engineering improvements (5-speed trans, VVT-i, more advanced ECU/fuel management, etc.) would be capable of.

The '99 is an impressive feat of engineering and a genuinely fine automobile. If this car were a professional boxer, it would be George Foreman. Old, reliable, somewhat overweight, probably no longer at its peak efficiency, but always ready and willing to go the distance. A few other words also come to mind; Solid. Powerful. Relaxing to drive. Certainly stylish in a dignified sort of way. Sound system (Nakamichi) sucks on FM, but CD's are stellar. The HID headlights kick %^*!! Popped the trunk, gave a yell... and it echoed... it's large enough that Jimmy Hoffa just might be in there and you'd never know it. Those of the female persuasion have expressed the interior combination of California Walnut and jet black leather apparently qualifies as quite 'sexy'. Sweet. No arguments here. B) Good thing it has a strong air conditioner, otherwise the combination of that black-as-night interior plus a northeastern summer would lead to some serious swelter. Right Guard would lose that contest every time. No one likes to look dignified yet smell like a Wildebeest.

Anyhow, I won't go on the record stating that I'm completely in love with the thing just yet since I've spent nearly as much time repairing the prior owners minor neglect as I have driving. Admittedly, this isn't the cars fault. Once the chassis restoration has been completed (box-o'-bushings inbound as we speak - among many other things) hopefully the car will grow on me like mold. Right now my early overall opinion of the ownership experience is pretty much neutral. I tend to keep cars a lot longer now than I used to, so time will tell. More on that later...

So, how exactly do you get 30+ MPG out of an LS-400 and put the EPA estimates to shame? Glad you asked. For those that have followed my various rants and inquisitions over the past month here on this forum, you're possibly already aware I've already changed out the fluids in the car from stem-to-stern. It's the first thing I ALWAYS do the moment I purchase a previously enjoyed automobile. Fresh oil and filter change. Flush the transmission with OEM T-IV fluid (man, is that stuff slippery). Mobil-1 synthetic 75w90 gear oil in the differential. All new sealing washers on every bolt that gets touched to help prevent leaks. Power-flush the brake fluid. Oh, and that was just the first 48 hours of ownership. Yeah, I'm pretty meticulous (or is that ridiculous?) about my cars... but trust me - it pays off at resale time assuming you can find someone who appreciates it. Maybe I just have too much free time.

Anyhow, I promise not to let this post stretch out 'til it resembles the book 'War & Peace', so I'll cut to the chase here. Assuming the onboard trip computer in the car is reasonably accurate (when filling the tank the gas pump seemed to agree), in mixed driving (city/rural back roads/bit of highway) the car is averaging right around 25mpg, admittedly going fairly easy on the throttle... especially until everything else is sorted out (Round-2: chassis bushings replaced, brake rotors cut with fresh pads, cabin filter, etc.). On a pure highway run with no stops it's showing a remarkable 32-33mpg steadily with premium fuel (of course), 36psi in the tires (less rolling resistance at the expense of a bit of ride quality - a fair trade in my opinion), windows up, no A/C, and the cruise set exactly at 70mph. I'm certain the reduction in frictional losses as a result of all top-quality lubricants throughout the drivetrain does play a significant role here. It all does add up. One slightly dragging brake caliper can also absolutely demolish fuel economy, just like a bad oxygen sensor, worn spark plugs, partially clogged fuel injectors, dirty air filter... the list is long and distinguished. Aggressive driving habits can also easily shave 5-to-8mpg off with no trouble at all. For some additional perspective - my buddies 2002 Corvette got 3mpg (yes... three) at wide-open-throttle... and 31 holding a steady 65mph. I get my cheap thrills on Japanese sportbikes so I feel no desire to flog this car. I didn't buy an LS to go fast. It's a living room with wheels. So far, I'd say I'm very pleased with the economy aspects, but I believe it can do even better. I intend to do some tests and dabble with lighter viscosity synthetic engine oils trying to safely eek out at least another mile per gallon. Maybe bump the tires up to 40psi temporarily...

Personally, I don't feel it is impossible to realistically get 35mpg highway out of this car while still maintaining the national speed limit. Right now, that's the goal. I'll keep tweaking... if it can be done, I'll definitely snap some photos to prove it. It kind of turns into a game where you're aiming for a new high-score all the time. And with that said, if you're still here reading this right to the end... I appreciate your perseverance. You really are a glutton for punishment! Just kidding. Actually, it would be great to hear about the experiences other owners are having with this generation (1998 - 2000) LS in particular, although anyone is certainly welcome to chuck in 2-cents worth. If you're in the neighborhood, stop by and we'll have a brew while discussing the finer points of valve overlap and injector duty cycles... 'Til next time....

[curiousB]

Well you can save another 8% by just running regular fuel. Its typically $0.20 more per gallon for premium yet it doesn't offer any appreciable MPG improvement over regular. At $2.50/gal on regular and $2.70 for premium that is 8% cheaper and a bigger single impact than most of your improvements.

[jcrome04]

Oh God please do not bring up which octane of fuel to use in the LS hahaha

The best MPG I have gotten in my 97 LS was 30.3

I do not believe 35 would be do-able. That is a HUGE stretch.

[Slvr99LS]

Well you can save another 8% by just running regular fuel. Its typically $0.20 more per gallon for premium yet it doesn't offer any appreciable MPG improvement over regular. At $2.50/gal on regular and $2.70 for premium that is 8% cheaper and a bigger single impact than most of your improvements.

Unfortunately I'd have to say I strongly disagree with your assertion that running 87 octane fuel in a high-compression, performance engine would somehow improve fuel economy or is a legitimate cost-effective means of reducing overall operating costs. Assuming the knock sensors were doing their job and preventing your money-saving decision from costing you an $8,000 short block, the ECU (commonly referred to at the computer) will !Removed! the ignition timing as required to prevent destructive detonation (pinging), at the expense of throttle response AND.... fuel economy. The Lexus LS engine, regardless of year, was designed and engineered to run most efficiently on gasoline with an octane rating of 91 or better - case closed. Yes, it will still physically run on lower grade fuels, and some may even claim to notice no difference, but my racing and dyno experience speaks volumes to the contrary. Personally, it's a risk I'd never willingly take. Automotive forums throughout the internet are chock full of discussions/debates on this specific topic. Perhaps you would do well to read a bit about it. Won't cost you a nickel. I didn't create the post "Maximum possible fuel economy" to argue with anyone, although your input is certainly appreciated. With that said, I was never looking at it solely from a financial standpoint. If I were I surely wouldn't spend the fortune I do on cars, oftentimes replacing components that haven't even failed or given any indication of problems. That's called 'preventive maintenance' and I'm their unofficial poster child.

In a nutshell, simply trying to determine what the maximum realistically obtainable mileage for an LS-400 under virtually ideal conditions is. Seemed like a fun thing to do that some others might enjoy reading about... or potentially even apply to their own vehicles. Some of the more basic concepts such as friction-reducing premium lubricants, correcting tire pressures, altering driving style, etc. can pay huge dividends regardless of vehicle year, make, or model.

There's definitely a certain psychological satisfaction to be had from wringing the most out of a well-tuned machine. Fellow 'gearheads' I'm sure will be nodding in agreement. Whether it's shaving 2/100th's of a second off a quarter-mile time... or squeezing ridiculous gas mileage out of a 2-ton land yacht with a high-revving V8 under the hood. Inquiring minds wanna know. I'll post further findings when I have them to share.

[SRK]

Given that the engine has a management system that is among the best in the world, the only way you can improve mileage is by driving style. And that would mean !Removed!-footing around and using very little throttle. Which would then mean very low cylinder pressures, and that means no need for high octane fuel, which is only advantageous at high cylinder pressures.

You would do well to study engine design (aircraft piston engines in particular), physics, and chemistry.

[curiousB]

Perhaps you would do well to read a bit about it. Won't cost you a nickel.

Actually I have a read a bit about it. Here are some quotes from experts in the field. Doesn't seem to make a strong case for premium.....

..."Prejudice and preference aside, engineers, scientists and the federal government say there's little need for premium."...

...""I personally use regular even though my owner's manual says you'll get better performance with premium," says Lewis Gibbs, consulting engineer and 45-year veteran at Chevron oil company. He's chairman of Technical Committee 7 on Fuels, part of the Society of Automotive Engineers (SAE) Fuels & Lubricants Council. Gibbs knows gas."...

..."The main advantage of premium-grade gas is that it allows automakers to advertise a few more horsepower by designing and tuning engines to take advantage of premium's anti-knock properties. But auto engineers generally agree that if you use regular in a premium engine, the power loss is so slight, most drivers can't tell."...

...""I go back and forth, and I'm hard-pressed to notice" whether there's regular or premium in the tank, says Jeff Jetter, principal chemist at Honda Research and Development Americas. He drives an Acura designed for premium.

Import brands, especially, use premium fuel to distinguish their upmarket models. Most Toyotas, for instance, are designed to run on regular or midgrade, while the automaker's Lexus luxury brand prefers (i.e. market positioning of brand rather than science) premium. Same with Honda and its Acura luxury line."...

..."Gasoline retailers and refiners like high-test because it's more profitable than regular-grade gas is. The retailer paid about 8 cents more for the premium you pay 20 cents more for"...

..."Today's engines use highly evolved versions of a device called a knock sensor to adjust settings automatically for low-octane gas. The engine control computers keep pushing to maximize performance on whatever grade of fuel is used."...

..."The only modern engines that should really need premium are those with superchargers, which force-feed fuel into the cylinders. "You're driving along and just &#33;Removed&#33; the gas and the knock sensor cannot sense the knock fast enough in some cases," because the supercharger boosts pressure so fast, says Bob Furey, chemist and fuels specialist at General Motors."...

..."Burning regular when the owner's manual specifies premium won't void the warranty, nor damage the engine, even the most finicky automakers say. "You're giving up perhaps just a little bit of performance that a customer wouldn't really even notice, it's so slight," says Furey."...

..."High-test does have a potential fuel economy benefit. It is slightly denser than lower-octane gas, meaning there's a little more energy in a gallon. But the small difference is hard to measure in real-world use, and that same density can contribute to undesirable buildup of waste products inside the engine."...

..."Guilt plays a part. Some people feel almost guilty, as if they are abusing their cars, when they don't burn premium, says gasoline retailer Jay Ricker, president of Ricker Oil of Anderson, Ind., which operates 28 stations. "They go all the way down to 87 (octane), but maybe every fourth tank they put in the good stuff.""...

[1990LS400]

Maybe stripping the interior and trunk down to bare metal would help you fulfill your 35 mpg fantasy. And there are plenty of heavy components under the hood that can go ... who needs A/C, ABS, power steering and the like? Get rid of the spare tire too. Put very skinny tires on the car and pump them up to maximum.

I usually drive quite gently and have tracked every gallon of fuel used in every car I have owned in the last 40+ years.

No matter what I have done, 27 mpg is towards the top of the range for my 00 LS at 70 mph. Yesterday, I filled up the tank and drove five miles at 45 mph or less for a total of less than five miles and 178 miles at a constant 70 mph with cruise control set. The trip computer for this 183 miles says the car has averaged 25.2 mpg. OK, I had a couple of airline carry-on size suitcases in the trunk but the car was otherwise lightly loaded.

My 00 LS400 has exceeded 30 mpg, and just barely, only once -- while driving from Tulsa OK to Kansas City with one of the stiffest tailwinds I've ever encountered ... a tail wind wind of as high as 50 mph.

Even my 4 cylinder Mercedes diesel sedan rarely broke 30 mpg at highway speeds -- I drove it from new to over 200,000 miles and tracked every gallon of diesel fuel that ever went into its tank. It usually averaged about 28 mpg at 70 mph.

35 mpg at 70 mph in a 99 LS400 is a dream. It's a nice dream but still a dream.

[jcrome04]

Let's please everyone just drop the octane topic. Let's pretend it never was brought up. If you want to find info on octane there are COUNTLESS threads of it on here. Just do a little searchin'. B)

Let's stick to the topic. Improving fuel economy.

One thing I can add is that if the coolant temp sensor has never been replaced... DO IT! That has a major effect on MPGs.

By replacing mine my daily AVG went from 17-18mpg to 20-21mpg

[eatingupblacktop]

Would you believe 33mpg out of a 3,900 pound automobile with nearly 300HP? Read on....

Actually, it would be great to hear about the experiences other owners are having with this generation (1998 - 2000) LS in particular, although anyone is certainly welcome to chuck in 2-cents worth. If you're in the neighborhood, stop by and we'll have a brew while discussing the finer points of valve overlap and injector duty cycles... 'Til next time....

Brew always sounds good and we could add low tension rings, crosshatch angles, and plateau bore finishes to the list ... in the meantime take a look at this link and maybe add your stats while you're there:

http://us.lexusownersclub.com/forums/index...showtopic=51747

[Brett in AK]

I have added Slick 50 oil treatment to each of my vehicles. I did it primarily for cold weather cranking, but they also claim an increase in fuel economy as well. Might be worth checking into. Quite honestly I'm not all that concerned about fuel economy. I drive a 98 JGC with the 5.9, a 05 Jeep Rubicon, a 49 Dodge Power Wagon. The LS was purchased for the luxury it offers. To each there own!

[aarman4]

I think it is easily doable.

Check out some of the driving habits of hypermilers.

Get behind a fair sized semi-truck pulling 1 or two trailers(make sure he has EXCELLENT mudflaps to protect the dirt from your beautiful LS's hood, if their is more traffic, even better, and then go easy on the gas. On hills, speed up as you go down them, and try to coast as much as possible when going up them (roller coaster effect). Inflate the living *BLEEP* out of your tires, take your extra trunk mat out, and your floor mats, and don;t eat before you drive ;)

Your driving habits will make more difference than you can imagine, and I do agree that very nice, clean, slick oils that are within the man. spec will do wonders for your MPG. Air filter will be another big one.

Good luck, i would love to see you break the mark!

[Slvr99LS]

Given that the engine has a management system that is among the best in the world, the only way you can improve mileage is by driving style. And that would mean !Removed!-footing around and using very little throttle. Which would then mean very low cylinder pressures, and that means no need for high octane fuel, which is only advantageous at high cylinder pressures.

You would do well to study engine design (aircraft piston engines in particular), physics, and chemistry.

Hey, now we're getting some input! That's what I'm talking about. Appreciate the recommendation SRK. Actually I have studied aircraft engines in my travels... some of my particular favorites being the multi-gang radials from the WW-II era. They're aesthetically beautiful and sound like nothing else on earth. Then there was the incredible Rolls-Royce Merlin V-12. What an engineering marvel right there. On a slightly smaller scale, just last week I got to spend a few hours in a single-engine Beechcraft Bonanza with a 285HP fuel-injected Continental flat-6. What a great aircraft!

Now, I agree with your statement on some counts... and disagree on others. I'll refrain from delving too far into a broadbased discussion and stick more to topic at hand... which is the Lexus LS-400. With a modern engine like this, depending on how wide a range of timing control the ECU has been given, even '!Removed!-footing' around at very minimal throttle apertures, utilizing a suitable fuel the ignition timing may be substantially advanced. Since the injector pulse width is also under ECU control, the mixture can also be leaned out beyond the stoichiometric ideal which will further take advantage of the additional anti-knock benefit afforded by higher octane. These are some smart engineers. Honda in particular has lots of experience building stratified-charge engines, even dating back to the 1970's with their original CVCC design which ran clean enough at the time to do without a catalytic converter. Now, what additional aspects of physics and chemistry would you like to apply here that have been overlooked? Looking forward to your response.

[Slvr99LS]

Would you believe 33mpg out of a 3,900 pound automobile with nearly 300HP? Read on....

Actually, it would be great to hear about the experiences other owners are having with this generation (1998 - 2000) LS in particular, although anyone is certainly welcome to chuck in 2-cents worth. If you're in the neighborhood, stop by and we'll have a brew while discussing the finer points of valve overlap and injector duty cycles... 'Til next time....

Brew always sounds good and we could add low tension rings, crosshatch angles, and plateau bore finishes to the list ... in the meantime take a look at this link and maybe add your stats while you're there:

http://us.lexusownersclub.com/forums/index...showtopic=51747

Blacktop (great name btw!), thanks for adding to the fun. Never expected this topic to branch off into so many different directions... not that there's anything wrong with that. Suppose I should've anticipated at least a minor lambasting for even THINKING that an LS could achieve 35mpg highway under nearly ideal conditions. But, as a forum veteran, you yourself have stated achieving as much as 33.29... and with an older model LS to boot. I don't mind being called a dreamer. Just don't call me late for dinner. Without dreams and high aspirations very little is ever accomplished in this world. I wasn't challenging anyone else to try for the 35 mark... I'm challenging myself. I also never even mentioned fuel octane initially other than to state I am using the fuel spec'd by the engineers who originally designed the car. A lively discussion is great - let's keep it going!

If 35mpg geniunely isn't possible, I'll post what the results were. It's my personal car that's the guinea pig, not someone elses. I would also never consider it a 'failure' if it doesn't happen... it's simply a learning experience which many can potentially benefit from. I also have no intentions of continuing to drive in a way which would customarily return this type of mileage. I'm a speed-freak... always have been. 9-second quarter miles aren't even all that exciting anymore... so mashing the loud-pedal on the LS isn't exactly a thrill. As they say on TV: This is a test. This is only a test!

P.S. Since you mentioned crosshatch angles and specific bore finishes... what are your thoughts on the break-in process for a freshly built engine?

[Slvr99LS]

I think it is easily doable.

Check out some of the driving habits of hypermilers.

Get behind a fair sized semi-truck pulling 1 or two trailers(make sure he has EXCELLENT mudflaps to protect the dirt from your beautiful LS's hood, if their is more traffic, even better, and then go easy on the gas. On hills, speed up as you go down them, and try to coast as much as possible when going up them (roller coaster effect). Inflate the living *BLEEP* out of your tires, take your extra trunk mat out, and your floor mats, and don;t eat before you drive ;)

Your driving habits will make more difference than you can imagine, and I do agree that very nice, clean, slick oils that are within the man. spec will do wonders for your MPG. Air filter will be another big one.

Good luck, i would love to see you break the mark!

Aarman, thanks for the vote of confidence... seems you're the first! In less than 24 hours I've been told it's a fantasy, I'm dreaming, to strip the whole interior out, told I need lessons in thermo-dynamics and chemistry, suggested I burn 87 octane (why not 85 then??), who needs A/C, power steering, etc.... which all just made me :D ear-to-ear of course. Man, I love these forums!

Interesting that you mentioned 'hypermilers', because I'll admit I have done some reading toward that end, and will concede they were part of my inspiration in the first place. Apparently the doubters far outweight the believers.... which naturally just inspires me even more to succeed. I'll pass on tailgating the stone-throwing 18 wheelers, thanks. And for the record, there will be NO modifications done to the car. Despite the suggestions to the contrary, the Nakamichi stays. The 225mm wide Michelins stay. All the seats... those stay too. And just so no one crys foul, I'll even eat a huge dinner before attempting the record run. B)

I'm genuinely serious about this, even if no one else seemingly is. Bet if gas were $5 clams a gallon right now this would be the #1 read thread on the entire forum. This same time last year some nutjobs on eBay were paying $7,000 for a 14 year old Geo Metro with a 3-cylinder gerbil mill under the hood because gas costs seemed to be escalating with no end in sight. 8-year old Honda Insights with 100K+ on the clock were selling for what they went for brand new. People were legitimately panicking. How quickly we all seem to forget though. Fact is, we have a finite supply of fossil fuels and it unfortunately won't stay cheap (a relative term) forever. In the meantime, I'm having some fun with this. Thanks to all who've already taken the time or enough of an interest to follow along.

[SRK]

The purpose of the O2 sensor is to maintain stoichiometric under all conditions, except wide open throttle, where overrich is used to protect the engine and briefly overheat the cats to clean them. The reason for holding stoichiometric is because at that point the three major pollutants are at their lowest. Leaner and NOx goes up, richer and CO and HC go up. It's the "sweet spot" for emissions in other words. Stratified charge, if it is used, is intended to keep mixture formation away from the cylinder walls and combustion chamber to avoid the cooling they impart, which raises HC.

So as the engine is programmed, without any chance of modification, to achieve perfect combustion within it's design limits, there is nothing to do but drive gently.

You may experience a "light load ping" with regular fuel, but I highly doubt it. Even if the engine did ping, the low cylinder pressure means it is quite benign, and will never damage anything.

I'm glad you understand aircraft engines. I'm a former pilot, and I am a member of the AEHS -devoted to historical aircraft engines. As you know ALL large displacement aircraft engine must now operate on 100LL fuel, which is far less octane than they were designed to operate on. And yet they still fly. Why? Because the pilots do not allow the engine to develop the boost that they used to - lower cylinder pressure saves the day. So no Merlin can produce 1900 plus horsepower today like they did on 130-145 octane fuels - they make 1400 on 100LL and are glad of it. Same with the big Pratts and Wrights. The boys at Reno run huge boosts, and blow the engines apart routinely, because of this.

Engines can't read - they don't know what the valve covers say. They just run, and the principles are the same. The wife puts 89 in her LS and it runs perfectly. I put 92 in my GS (94 is available where I live) and I beat the hell out of it. No pinging.

Static compression ratios are not the same as dynamic, which constantly change according to throttle opening and rpm, unlike diesels, which nearly achieve the static CR at all times.

Whew.

[aarman4]

With our gas in Canada comparing to $3.81 per US Gallon ($1.10CDN/L), on occasion I have been hypermiling with my very old beaten up little 1985 Nissan Kingcab truck, and let me tell you, I imagine it will be much harder with an automatic transimission, and perhaps not as fun either, but I think you can do it for sure.

Best of luck, and please do keep me informed. I highly recommend getting a few friends to join you for a long road trip during your trials, and drive in proximity to you on the highway, and maybe even give them a quick lesson in hypermiling ahead of time so you do not have to drop the hammer to keep up.

PS - Very happy to see you value your paint, I cannot stand the shrapnel those big trucks toss at me

[Marklouis]

Please fellas, lets not "Draft" behind 18 wheelers on the interstate. for one truckers really REALLY hate that, and big rigs are designed to stop quickly with a heavy load. if they have a reason to slam on the brakes, even your Bruce Lee reflexes will not save your LS transforming into an instant convertible, let alone take your head off. if you cant see the side mirrors of the big truck...back off or go around them.

its better to be safe and healthy than save a few dimes on gas...

...otherwise, i agree with those that want to save gas, just keep your foot out of it..eezy peezy...and good maintanance.

i average 21-24 mpg, within rush hour traffic and A/C on.

[aarman4]

Please fellas, lets not "Draft" behind 18 wheelers on the interstate

Not once did I say to draft, just be behind. I think Tailgating is the single most frustraiting thing one can do to the driver in front of them. Having the truck out there, as well as other vehicles around distrubs the air on the road you are travelling. The more disturbed, especially in the direction of travel, the better for your fuel economy for this aspect of the drive.

[Slvr99LS]

The purpose of the O2 sensor is to maintain stoichiometric under all conditions, except wide open throttle, where overrich is used to protect the engine and briefly overheat the cats to clean them. The reason for holding stoichiometric is because at that point the three major pollutants are at their lowest. Leaner and NOx goes up, richer and CO and HC go up. It's the "sweet spot" for emissions in other words. Stratified charge, if it is used, is intended to keep mixture formation away from the cylinder walls and combustion chamber to avoid the cooling they impart, which raises HC.

So as the engine is programmed, without any chance of modification, to achieve perfect combustion within it's design limits, there is nothing to do but drive gently.

You may experience a "light load ping" with regular fuel, but I highly doubt it. Even if the engine did ping, the low cylinder pressure means it is quite benign, and will never damage anything.

I'm glad you understand aircraft engines. I'm a former pilot, and I am a member of the AEHS -devoted to historical aircraft engines. As you know ALL large displacement aircraft engine must now operate on 100LL fuel, which is far less octane than they were designed to operate on. And yet they still fly. Why? Because the pilots do not allow the engine to develop the boost that they used to - lower cylinder pressure saves the day. So no Merlin can produce 1900 plus horsepower today like they did on 130-145 octane fuels - they make 1400 on 100LL and are glad of it. Same with the big Pratts and Wrights. The boys at Reno run huge boosts, and blow the engines apart routinely, because of this.

Engines can't read - they don't know what the valve covers say. They just run, and the principles are the same. The wife puts 89 in her LS and it runs perfectly. I put 92 in my GS (94 is available where I live) and I beat the hell out of it. No pinging.

Static compression ratios are not the same as dynamic, which constantly change according to throttle opening and rpm, unlike diesels, which nearly achieve the static CR at all times.

Whew.

Whew is right! Good stuff though, and very interesting information on how they keep those irreplaceable warbirds in the air on todays fuels. I actually did take note of the 100-octane low-lead fuel available at the airport last week, but didn't realize there's nothing else available.

On another note, curious why with all that's been stated in this particular thread, you and your wife don't run 87 octane in your cars? Personally, I'll stand by my prior assertion and continue to pony up and pay for the 'good stuff'. As another post suggests, I'm sure the big oil companies appreciate the pad to their quarterly profits.

Shifting gears here and getting back to the core intent of the thread, another LOC member mentioned here the term 'hypermiling', and I may have to employ some (but definitely not all) of their techniques to achieve 35+mpg from the Lex, but yes I do believe it is a very realistic goal and can be done. One commonly used method is called P & G (Pulse/Glide) which is apparently very effective when applied correctly. In a nutshell it involves accelerating to a given speed, coasting for a period, then repeating. Hills and valleys can also be used to ones advantage. During 'coast mode', most modern fuel-injected vehicles completely shut off the injectors. Spark continues, there's just no fuel there to burn. I do know my instantaneous mileage on the trip computer goes immediately to '99.9' when the throttle is lifted. If you throw the car in neutral and allow it to coast, fuel is still being burned at idle, although you remove the parasitic drag of the engine itself so it may or may not be a wash on that count. Some experimentation is in order. I doubt I'll be able to do it safely on the freeway without getting plowed by a Peterbilt and/or pizzing off plenty of people, but for rural driving on lightly traveled backroads, seems it works very well. Either way... like I've maintained all along, it's going to be fun to find out. I've spent a lifetime going fast, what's wrong with a few days of going slow? I'm not looking to get crazy with this, just find out what's possible with relatively minimal effort and expense. Toward that end, here's some cool info I found on Wikipedia: http://en.wikipedia.org/wiki/Fuel_economy_...ng_technologies

Straight off they mention low-friction lubricants, which is a great starting point I'm already pursuing. More to follow...

[Marklouis]

Please fellas, lets not "Draft" behind 18 wheelers on the interstate

Not once did I say to draft, just be behind. I think Tailgating is the single most frustraiting thing one can do to the driver in front of them. Having the truck out there, as well as other vehicles around distrubs the air on the road you are travelling. The more disturbed, especially in the direction of travel, the better for your fuel economy for this aspect of the drive.

I didnt say you said to draft....in fact, i was not replying to your quote at all aarman. B)

[jcrome04]

Hmm I didn't even consider the God awful art of "hypermiling"

I wouldn't be shocked to see 35mpg if you did THAT.

But from just !Removed!-footing your LS you WON'T get 35MPG... That's 787.5miles to my 22.5gal tank for 35mpg.

[Marklouis]

Hmm I didn't even consider the God awful art of "hypermiling"

I wouldn't be shocked to see 35mpg if you did THAT.

But from just !Removed!-footing your LS you WON'T get 35MPG... That's 787.5miles to my 22.5gal tank for 35mpg.

if and when i get at least 500+ miles to my tank when traveling with a little left to spare, im a happy man. B)

[Csosz74]

Hey guys,

just my experience with my 1990 LS400. With my 'normal' foot, I got 20 mpg. With VERY careful foot, 35 miles an hour, 65 on freeways, no 'shooting out' :P at green light, I got 21 mpg.

What about the tuning chips? Anyone tried one of them? They supposed to boost the horsepower and get better milage?

Or we're talking about without modification?

just a thought

A

[eatingupblacktop]

Would you believe 33mpg out of a 3,900 pound automobile with nearly 300HP? Read on....

Actually, it would be great to hear about the experiences other owners are having with this generation (1998 - 2000) LS in particular, although anyone is certainly welcome to chuck in 2-cents worth. If you're in the neighborhood, stop by and we'll have a brew while discussing the finer points of valve overlap and injector duty cycles... 'Til next time....

Brew always sounds good and we could add low tension rings, crosshatch angles, and plateau bore finishes to the list ... in the meantime take a look at this link and maybe add your stats while you're there:

http://us.lexusownersclub.com/forums/index...showtopic=51747

Blacktop (great name btw!), thanks for adding to the fun. Never expected this topic to branch off into so many different directions... not that there's anything wrong with that. Suppose I should've anticipated at least a minor lambasting for even THINKING that an LS could achieve 35mpg highway under nearly ideal conditions. But, as a forum veteran, you yourself have stated achieving as much as 33.29... and with an older model LS to boot. I don't mind being called a dreamer. Just don't call me late for dinner. Without dreams and high aspirations very little is ever accomplished in this world. I wasn't challenging anyone else to try for the 35 mark... I'm challenging myself. I also never even mentioned fuel octane initially other than to state I am using the fuel spec'd by the engineers who originally designed the car. A lively discussion is great - let's keep it going!

If 35mpg geniunely isn't possible, I'll post what the results were. It's my personal car that's the guinea pig, not someone elses. I would also never consider it a 'failure' if it doesn't happen... it's simply a learning experience which many can potentially benefit from. I also have no intentions of continuing to drive in a way which would customarily return this type of mileage. I'm a speed-freak... always have been. 9-second quarter miles aren't even all that exciting anymore... so mashing the loud-pedal on the LS isn't exactly a thrill. As they say on TV: This is a test. This is only a test!

P.S. Since you mentioned crosshatch angles and specific bore finishes... what are your thoughts on the break-in process for a freshly built engine?

Depends on a few things:

1. Who did the rebuild - If it's a top pro and it's built right, consensus is it'll run well regardless of "break

in" style. No matter what method you use, it won't remedy a bad build or bad parts used in the build. Cross hatch/cylinder finish on the cylinder bores should match up with piston rings used.

2. Are you racing - Typically race engines get broken in on the dyno under full load at wot. However, race engines get rebuilt every 20k or so. Unfortunately without a teardown after a breakin on the dyno, you can't tell what the session has done to your engine in terms of longevity for an engine expected to go 100k plus.

3. What type of engine - Porsche engines are run pretty hard at the factory for testing and break-in purposes, and don't require further break in. Vipers and Corvette's come from the factory with synthetic oil containing a high level of zinc. This may be ok for breaking in high performance engines running 500 to 600hp with chrome moly piston rings, but not for your average 180hp stock v6 low performance production engines with cast iron rings. Every oil change should use dino oil, not synthetic, because synthetic is too lubricated and doesnt allow the rings to seat properly. There is also special break in oil available. You want the engine to wear during the break-in process, but you don't want shavings in the engine for very long. There will be a high level of insolubles in the oil so the more you change oil and flush, the better. I know someone who does uoa's on the first half dozen drains after a rebuild.

4. What is your intent - A typical breakin for someone intending on getting performance from there car or spending time at the track could look something like this:

30 second engine run at idle... CHANGE OIL & FILTER

20 Mile hard run, WOT, coast down, WOT.... CHANGE OIL & FILTER

50 Miles varied driving, hard driving alot of time... CHANGE OIL & FILTER

200 Miles driving with varied load.... CHANGE OIL & FILTER

Not sure what this will do for longevity.

5. Is longevity a priority - A common mistake people make with a new motor is idling. New engines should be driven to break them in right after the rebuild. The first 20 to 40 miles are the most important for ring and valvetrain seating. The rings will not seat any further after that. If proper seating doesn't take place, the engine will lose power and longevity. Loaded and revved through the entire range, engines do require to be stressed during the breakin period differently from other systems such as the tranny, clutch, diff, brakes, where a gentler approach would be well advised.

6. My advice:

- Do the drains at 100, 500 and 1000 miles and check for shavings in the filter.

- Do a compression test at 50 miles. Also check oil consumption.

- No cruise for the first 500 miles

- Constantly vary your driving speed for the first 500 miles or at least go between different gears at the same speed.

. No constant RPM.

- No short drives for the first 500 miles

- For the next 500 miles continue varying the speed but every so often with moderate aceleration take it to the redline and decelerate back down the same way as on your way up. I would even do this in each individual gear. Running it up in gear and let it slow down in the same gear from a higher rpm, sucks the piston ring back allowing it to seat well on both sides.

- No idling for the first 1k

- No hard aceleration until the engine reaches proper operating temps.

Having done 9 sec quarters, I'm sure you've heard the following:

"I love motorsports because all other sports require only 1 ball!"

;)

[Slvr99LS]

In the quest for maximum fuel economy, as well as enhanced engine performance, one of the simplest, least costly places to look is your air filter. Shown below is a picture of the actual filter element recently removed from my LS. Pretty easy to figure out which is the old, and which is the new. Lord only knows when the last time that thing was changed! Most amazingly, this was a Lexus dealer-only maintained car for at least 80+% of it's life (I have the maintenance records). Perhaps even factory trained technicians don't customarily check every customers filter if no problems were reported. Worth bearing in mind.

This thing is so nasty you could grow mushrooms from it (see below). Upon close inspection of the filter there are dead bees, other insects, leaves, grass clippings, sand, and plenty of unidentifiable grime and debris all lodged in the pleats. It certainly did its job, as the engine intake side was still remarkably clean. If the factory filter didn't have such a large surface area I suspect this amount of contamination would've affected performance and mileage long ago. And it only takes 5 minutes to replace.

On another note, this evening I replaced the original sway bar bushings to help restore the factory ride quality. The interesting part is that the OEM Lexus bushings come completely coated with a thin, dry-film lubricant to help prevent squeaks at the body-to-bushing, and bushing-to-swaybar interface. I'd never seen that done before. Indicative of the great attention to detail the engineers lavished on these cars. Briefly contemplated firmer aftermarket polyurethane replacements... but nope - decided on keeping it all original.

Permission to vomit granted....