Fuel Grade Choice

[aqbill]

Dear Fellow Enthusiasts, I recently purchased a 2006 CPO Crystal White on Cashmere LS430 with Nav and ML - and 62,000k on the ODO. Looking forward to seeing to what I can do fuel-efficiency wise. First question that occurs to me is one I'm sure has been covered before but I could not find anything using the search function. What fuel octane grade do you recommend? My most recent "other car" is a 2004 Audi A6 that recommends premium but seems to run just fine on either regular or mid-grade. It has FWD and CVT and has given years and many miles of great service. Also, any other tips for good gas mileage would be most welcomed.

[curiousB]

Dear Fellow Enthusiasts, I recently purchased a 2006 CPO Crystal White on Cashmere LS430 with Nav and ML - and 62,000k on the ODO. Looking forward to seeing to what I can do fuel-efficiency wise. First question that occurs to me is one I'm sure has been covered before but I could not find anything using the search function. What fuel octane grade do you recommend? My most recent "other car" is a 2004 Audi A6 that recommends premium but seems to run just fine on either regular or mid-grade. It has FWD and CVT and has given years and many miles of great service. Also, any other tips for good gas mileage would be most welcomed.

Well this question is sure to bring out many passionate opinions. I've run regular fuel in my '04 LS430 for two years and the engine has yet to fall out. I feel premium octane fuel is just a revenue grab by oil companies.

[aqbill]

Thanks for the quick reply. Have you noticed any change in fuel efficiency or performance? I see that you are in Chicago. How does your Lexus drive in snow or ice compromised conditions? Thanks again! :)

[curiousB]

Thanks for the quick reply. Have you noticed any change in fuel efficiency or performance? I see that you are in Chicago. How does your Lexus drive in snow or ice compromised conditions? Thanks again! :)

Well I don't really think this car is very good in snow. In general I find all rear wheel drive cars are poor in snow. I prefer front wheel drive as the drivetrain weight is on the drive axle. I know some people around here put 300-400 pounds of water softener salt in their trunks for winter and in the spring just dump it into their softener.

As for fuel efficiency comparisons. I haven't noticed any degradation of fuel efficiency with regular fuel. I do notice the 10-15% price uplift of premium though. Both fuels have about the same available energy of 111,400 BTU/gal so its misleading information that premium has higher energy density that regular. Certainly not 10-15% more (available energy) so its $/mile travelled is worse than regular.

Its a personal choce though. I guess if you're fortunate enough to afford a car of this type a slgiht premium on fuel isn't likely going to kill you. To each his own.

[jainla]

No the engine will not grenade if you use regular gas; but it will burn more fuel. The car will adjust automatically to whatever grade you put in it; although lower octane will yield less power and slightly poorer mileage. Also the throttle response won't be as crisp; but try it yourself and see if you think the compromise is acceptable.

Here in CA premium is about 20 cents a gallon more than regular; after spending ~$60 to fill up the car another $5 seems inconsequential.

The biggest jump in FE I got was when I changed the spark plugs and my mechanic cleaned out the throttle body. My average MPG went from 18 MPG to 20+. Also avoid heavy traffic, have your tires rotated and balanced, keep an alignment etc etc.

Welcome to the club!

[xrayangiodoc1]

Dear Fellow Enthusiasts, I recently purchased a 2006 CPO Crystal White on Cashmere LS430 with Nav and ML - and 62,000k on the ODO. Looking forward to seeing to what I can do fuel-efficiency wise. First question that occurs to me is one I'm sure has been covered before but I could not find anything using the search function. What fuel octane grade do you recommend? My most recent "other car" is a 2004 Audi A6 that recommends premium but seems to run just fine on either regular or mid-grade. It has FWD and CVT and has given years and many miles of great service. Also, any other tips for good gas mileage would be most welcomed.

I tried to economize on fuel by using half premium (93 octane) and half regular (87 octane). I figured that the octane would average about 90 and be a better deal than the midgrade 89 octane fuel. The car seemed to run fine but after about a year I noticed moderate hesitation that required an injector cleaning by the dealer (under warranty) and the advice to stick to premium grade which I have since done.

In regards to the winter driving issue (I live in the Buffalo, NY area), I put a set of Goodyear Assurance tires on and have been very pleased with the traction on snow. The tires seem to be very close to snow tire performance but are all-season. Wet weather performance has been excellent and the tire wear rating is about the highest I could find in a performance tire.

[landar]

I recently went on a 2k mile trip in my '02 and tried several tanks of regular just to see what the difference might be. The engine seemed to run the same. The mileage did seem slightly better (1 mpg) with premium. However the difference was so slight and the test so uncontrolled as to be statisically insignificant. However, I still run premium in the tank on a daily basis primarily because Lexus specifies it and premium is always only 20 cents more per gallon in my area no matter the base price of a gallon of regular. That means that as gas prices rise, premium becomes cheaper as an incremental cost adder. Twenty cents on $3.60 gas is 5.6%. It always costs me $4.00 more (20 gal @ 0.20) each time I fill with premium vs. regular. I have proven to myself that premium is less prone to gumming up(additives) than regular. And the manufacturer recommends it... and its always only $4.00 more each fill. I can afford that, so for me, premium is justified.

[VBdenny]

Perhaps it isn't as much about which octane to buy but rather about which brand to use. I use only top tier fuels such as Shell, BP, Exxon, Sunoco, Mobil, etc. Cheap gasoline is exactly that. I figure if the car says to use Premium, they had a reason for it so I do. I'm sure it would run on regular but as the curious one said, to each their own.

[SW03ES]

I wouldn't run regular in the LS...

[Mike Hobbs]

Everyone is entitled to their opinions, of course, but the detonation, detergent, and many other characteristics of gasoline are regulated for the various regions of the Country by Federal Law. Gasoline for each region is essentially the same within an octane group (e.g.91-93) regardless of the price paid. Why do I say "essentially"? Because specific brands may add coloring dyes or minute quantities of "special additives" that one would be hard-pressed to demonstrate as effective in achieving any specific utility. It's about marketing. They may not violate the law and change the essential qualities of the fuel. Your fuel is supplied by the nearest refinery, of course. It's very expensive to truck the stuff around.

As to the octane rating for a high-compression engine: Obviously, resistance to detonation is required...therefore the higher octane rating.

Compression naturally decreases as the engine wears, so the sensor that changes the spark timing may not need to function when low octane fuel is used. Personally, I use 91 and the cheapest I can find. Those stations usually sell higher volumes, have fresher fuel and probably more frequently-changed filters.