Regular Or Premium Unleaded Fuel?

[rollout]

Lexus recommends Premium (91 octate) fuel for my "new to me" 2000 GS300. Anyone tried using Regular (87 octane) or mid-grade (89 octane)? What, besides pinging could I expect from using the lower prices and lower octane grade?

I have not seen any posts on this topic before and would appreciate some tecnical as well as non-tech replys.

Thnks.

[SKperformance]

i am suprised there are no previous posts

i just replied to one last week

try an open search in more than the gs section

that may e the difference to get some point of views

i say premuim and nothing else

[E Dawg]

I say premium as well. Also note that the lower grade fuel burns quicker and I have heard that your car will not perform to it's peak capabilities. You do not want to put anything cheap in that expensive car of yours? :D

[anewname]

Besides pinging? You make it sound like it's no big deal. :P Precombustion is a serious matter, in my opinion. Use the premium, or you'll lose performance too.

I use 91 octane as a minimum. When I'm taking a long trip or something I use 94.

-Dave

[martialartsguy]

any one that tells you that it does not matter what fuel of octaine is a complete jerk off, its plain and simple the better octaine the better proformance, dont every go lower, your car will feel sluggish,

[rollout]

Here is some info I found on Engine Pinging:

In a normal non-pinging engine, the spark plug fires at the desired time and initiates a flame that moves across the combustion chamber consuming the air/fuel mixture as it goes. This flame increases the temperature and pressure in the cylinder and creates your power. When the combustion chamber temperatures get high enough, it is possible for the air/fuel mixture to spontaneously combust (pre-ignition). This is what happens when a car "diesels" on runs on after the ignition is turned off. Commonly the source of the ignition is from carbon deposits or simply a sharp edge on the piston or head surface.

When both pre-ignition and regular ignition occur simultaneously, you get two flame fronts moving towards each other. When they meet, they extinguish each other with a loud pop. That pop is the ping. This effect is similar to turning off the acetylene on an oxy/acetelene torch. The ping is not harmful. But it is an indication that there is something amiss, something that may be silently damaging you engine.

One source is excessive carbon buildup. That means nothing is wrong and the engine simply needs a good cleaning, ON THE INSIDE. The reason for the excessive carbon could be due to an oil consumption problem, either leaky valve seals or worn piston rings. Either way, the head needs to be removed to solve the root cause, the can be decarboned at the same time. An engine is normally good at burning away carbon on it's own. The problem could also be due to mal-adjusted carbs or a dirty air filter causing the engine to run way to rich. Again, that is a problem that needs correcting and a 1/2 bottle of Techron engine deposit cleaner will quiet it right up. In no case does the pinging from carbon cause engine damage.

The other cause of pinging is excessive cylinder temps. As the temps rise, the sharp edges of the piston will ignite the mixture. The excessive temperature will also start to melt the piston. Again this could be due to a number of situations. One case would be a dirty air cooled engine or a water cooled engine with some problem with the cooling system. The other possibly is that engine was designed to run that hot (like a race engine) and simply needs higher octane. This will in time cause engine damage, but it is again and indication of a problem. If the engine is dirty, higher octane will cause the pinging to go away, but it is still running too hot.

Contrary to what the gasoline companies advertise, engines never need to change octane. If a new engine is happy with 87 and at 40,000 miles starting pinging, that means is time for some maintenance, not higher octane. Many european cars and bikes need higher octane because of their better fuels. The US has the "worst" fuel in the world. Germany starts the fuel grades at 96 octane, the their engines are designed to need it. Now, many foreign manufacturers "de-tune" their engines to run on our 87 octane gas. If your engine needed 89 or 92 octane new, then that is what you must run. If it didn't need 92 new, and does now, look for a problem.

Now on the subject of a properly tuned engine pinging. Yes, they should ping, a little under certain conditions. Engineering is a field of compromise. You want the most power, the best fuel economy, the cleanest emissions, and the longest longevity out of any engine. But each of these conditions requires different tuning, generally opposite from each other.

An engine needs to be tuned to operate at a sweet spot that is the compromise of all requirements.

As I said earlier, pinging can be the result of high combustion temps, and this is the type you would expect to occur. High temps are caused by a combination of lean fuel and advanced timing. Lean fuel produces higher combustion temps and hence more power. It also produces higher emissions and potential engine damage.

When the engine is under sever load and a low RPM (like climbing a steep hill in top gear) then engine temperatures rise and will begin to ping. That is normal. That is desired. Yes, you are damaging the engine and melting the piston. (More on that later). That means that you have crossed the line are no longer is that compromise zone. That is good because engines are not meant to be operated in that fashion. PINGING MEANS IT IS TIME TO DOWNSHIFT.

Engines, particularly motorcycle engines, make their power in the upper 1/3 of the RPM range. If you are under sever load, you want the tachometer up near red line. That is where the engine was designed to run and it is by far the easiest on the motor. When you are lugging an engine, the oil pressure drops and the piston rods begin hammering against the crank shaft because there is no longer a high-pressure film of oil to prevent it. Likewise, the crankshaft in turn hammers against the block (or case). In either case, the damage you are doing to the bearings is far worse than the slight amount of aluminum being burned away. If you switch to a higher octane fuel to prevent the pinging, you may not realize you are destroying your bearings.

You could also !Removed! your timing or richen the carbs to prevent pinging under severe load on whatever octane gas you desire. But again, this will mask the bearing damage you are doing. It also moves the threshold of that "sweet spot" downward. Now you will not have pinging under sever load, but you will also not have complete combustion under normal conditions (such as cruising), and that can lead to poor fuel economy and excessive carbon deposits.

In a nutshell, the engine should ping if properly adjusted, under low RPM, severe load conditions. Next, you should use your transmission to avoid those conditions.

Lifted from a reply by Larry Piekarski

I quess I'll pony up for the 91 octane.

Thanks

[Lkevon]

or you can mix a 50/50 mixture of mid and premium grade to save that extra penny :) to get 91. but i would rather spend the little extra $$$ for my lex!!!

[jzz30]

remember that we have LUXURY cars meaning that we shoud spend a little extra money on things that we normaly wouldnt need to on a economy car like gas. so just put in the 91

[arsmtts]

I actually sell racing fuels and octanes. I would take exception to the U.S. having the worst fuel in the world. That would be China and India. It is true though that the octane values fo fuels do tend to be higher in Europe.....

If you have modified the engine such that it requires higher octane or Nos, then you already know you need a higher octane fuel. Otherwise, using the Fuel recommended by the manufacturer is critical to maintaining your warranty. If your warranty has expired, please continue to use the recommended fuel - with the following considerations:

As previously discussed, pinging or clattering can result from a build up of carbon deposits - which can increase the compression ratio (and heat) in the cylinder. If the warrenty has expired and pinging starts, the engine may have had an increase in octane demand - beyond the the octane capacity of the originally recommended fuel.

The engine needs decarbonizing or a tune up. Extended operation with pinging or clattering can (and probably will) cause engine damage over time. Service the vehicle and see if this stops the pinging. If it doesn't, go to the next higher level of octane, or try fuel from another station.

[MrSypher]

I only use Sunoco Super 94 octane....

[Lexus = sexuL]

Surely it's been asked before, but which grade of gas is most recommended?

Some friends say to fill up once a month with the high octane stuff, and use mid-grade the rest of the month.

Others say mid-grade all the time is sufficient.

???

[es3doubleO]

In my 92 ES I use 92 octane all the time.

[E Dawg]

I only use Sunoco Super 94 octane....

Where can you buy 94 octane? Is it at some special super gas station or what?

[MrSypher]

Only Sunoco Gas Stations sell 94 out here...

[steviej]

use what it says in you owner's manual.

steviej

[SW03ES]

I agree, the owners manual specifies premium, I always use premium.

[amf1932]

Here is what it says in my 2003 ES Owners Manual.

[FLiP Sp33d]

exxon 93 octane @ $1.89 9/10th per gallon

[SW03ES]

Wow Alan, I must have buzzed right over that, I thought it specified 91 or higher only...

Nevermind then, I suppose you can run 87 with no problems.

[amf1932]

I just took a trip from New York City to Minnetonka, Minnesota. I was using the regular grade of gas on my way out and premium grade on the way back to see if I noticed a performance difference. I did this to check whether the transmission operated any better(shifting hesitation) with the premium over the regular. Well, it didn't perform any better as far as I was concerned! There was no difference as far as mpg.....I averaged between 27.5 and 29.5 mpg at speeds between 65mph and 85mph. This I might add was mostly turnpike driving. I never heard any pinging going up the Allegheny mountains of Pennsylvania with the regular gas! The car had 1500 miles on the odometer when I started this trip and I ended up with about 4700 miles. Aside from the tranny glitches the car ran beautifully. I can't wait to get out on the open road again. :)

[bbsal]

same here!i only use sunoco 94 its the best around here!

[zeta]

i personally use 93 octane in my '93. basically because i've been bred to use premium for premium cars. :D

[bbsal]

94 octane sunoco here!i never use anything less.pay extra now save extra in the long run!

[steviej]

SW03ES, it is very odd,

the 02 and 03 are basically the same car with the addition of adjustable pedals in the 03.

BUT:

the 02 manual calls for premium and says a lesser grade could be used in a pinch.

the 03 manual calls for regular grade and says to use premium for improved performance.

My guess is too many people complained that they "had" to buy premium so the coorporate suits reworded the section to quiet the masses and keep their behinds covered.

steviej

[SW03ES]

Really Steve? I looked at mine, and sure enough it does say 87 is acceptable. Maybe its something as simple as a reprogram of the ECU between the two years. Probably like you said, people couldn't understand why the ES required premium while the Camry did not.

Actually, there's no difference between the 02 and the 03, because none of the 03s even shipped with the adjustable pedals. Mine doesn't have it, and I couldnt find one that did.