Yikes! In my 1998 ES 300 even though the manual said Premium, we used regular the last 65,000 miles (the car had 165,000 when we turned it in for the LS460L) without any problem...in fact in 10 years and all that mileage the only repairs we had were the timing belt replacement at the standard 100,000 and the spark plug wires when the volves ate the wires and a few light bulbs.

So my question is, the manual says 91 octane, but I know it has an on board comptuer that adjusts it to maximize the performance regardless of the octane....so can I use midrange 89 octane which is about 10 cents a gallon more than the regular, rather than the 30 -40 cent more 91? I guess it might be dumb to want to save 20-30 cents a gallon on this costly of a car....but I am tempted!

 

I've never used anything below premium on any of the Lexus' I've owned in the last 11 years. Then again, why would paying for premium gas be an issue for you if you can afford an LS?

 

You should be able to run 89 octane and most likely 87 octane with no damage to the engine. There will be a some loss of power and a slight reduction in mileage (but not nearly enough to offset the 30+ cents per gallon savings). If you should hear any engine pinging while running a lower octane, then definitely go back up one grade.

 

Let me get this straight - you have spent at least $64,000 (for a base LS) and you are thinking about scrimping on the gas to save money...

Seriously, you won't hurt anything but you will not have as much power. And, according to a Lexus factory Rep, the gas mileage will suffer.

 

Run premium fuel. You're going to get lower gas mileage and power. You're only paying a few bucks more at the pump (probably $3 or so). In the end, it almost evens out in fuel economy (regular vs premium) so why not run what the car wants?

 

you can even run 87 in it, the computer will just retard the timing to "use" those gas.

but man, you drive a 70k car and care about that 200 bucks extra for gas a year?!

 

Everyone here is correct. The knock sensor will adjust the timing to compensate for the lower octane. The reverse also applies. If you use higher octane, you will gain a tad bit of power. I run 96 octane in my GT500, even though it is tuned for 93. I rather spend a little more and not worry about detonation.

 

If the guys who made this car couldn't convince you to buy premium, then I dont think anything we say will have an impact.

Good luck a few years down the road. Feel free to read the 100,000 threads about premium vs. regular.