gas type for '98 ES300?

I was advised without asking by my dealer on my 2003 ES to use regular if I wanted to and save money. The engine makes adjustments for the slightly lower octane. I have 15K on my car now using only regular and have had no problems. Unless you have a high perfomace vehicle I doubt if it makes a whole lot of difference.

I've tried both types in my IS200.

I consistently get one more mile per gallon on high octane (normally Shell optimax) - so it just about pays for itself. I can't honestly say I've ever noticed any change in performance though.

PS - The "best" fuel seems to be BP Ultimate - I get the same mpg advantage described above, plus a smoother engine. Its a pity Shell stations are a lot easier to find than BP ones in the Bristol area of the UK.

You could do what I do. I put in 50% 93 octane and 50% 87 octane to get 90.5 which is close enough to the recommended 91. Sometimes I even tweak it a bit toward the 93 to really get 91. It requires two credit cards at the pump (it won't allow you to use the same card twice in a short period of time), and you have to learn how many gallons are required from the various points on the fuel gauge. Not a big deal. The cost ends up being the same as for "mid grade" which is merely 89 octane in most places. In other words, for a little extra work, you can get 90.5 octane for the same price as 89 octane.

Yeah, I squeeze the buffaloes and drive a Lexus. A contradiction? I would argue that this is HOW I GOT TO DRIVE a Lexus!

If you mix 50% 93 octane and 50% 87 octane you should get 90 octane. I use to do this all the time for two SC400's I owned except I mixed 50% 93 octane and 50% 89 octane to get 91 octane. I never had a problem using the same credit card (most of the time a Discover card) for two purchases one right after the other. Maybe your credit card has different rules.

David