95 GS300: Gas type: unleaded, premium, super?

best performance, i just got it used and i am wondering which gas type, or combination of gases is best for my car. Thanks,

This answer refers to the 98 Lexus GS 300, which is the same basic engine but up dated with VTEC etc. Around town with light loads and slow to medium acceleration I don't think it makes much difference. But on the highway at speed and in passing performance is much improved with premium. I have found that for long highway travel, around 80 MPH, normal traffic etc, the MPG of premium is more than enough to pay for the increased cost. Our 98 GS300 gets

25-28 with premium on the highway, 19-21 on regular, and 21-23 on mid grade. ***************** Only in America...... do we use the word 'politic's to describe the process so well: 'Poli' in Latin meaning 'many' and 'tics' meaning 'bloodsucking creatures'.

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Previously in alt.autos.lexus, KG proclaimed :

best performance, i just got it used and i am wondering which gas type, or combination of gases is best for my car. Thanks,

VTEC is Honda technology

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Higher octane gas (super unleaded) does not give your car more power or better fuel mileage. It means your car is more resistant to detonation. Purchasing the more expensive, higher octane, premium fuel provides no benefit to most cars. The only reason to use high octane gas is if your car is starting to "ping" (which most modern cars won't do any more due to intelligent ECU's that retard timing, reducing power to avoid pinging).

use for best performance, i just got it used and i am wondering which gas type, or combination of gases is best for my car. Thanks,

creatures'.

And if you reduce power, it means what? You must increase fuel use to maintain the same speed with the same load. That is why with some engines you will get better MPG with a higher octane. The trick is to determine if the increased cost of the fuel is less than the increase in MPG.

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I think it is a mis-conception that lower-octane fuel reduces fuel mileage. If the knock sensors kick in and detune the car at full power, yes, power is reduced, but only peak power, not the normal power used in day-to-day driving. In fact, lower-octane fuels actually have a slightly higher specific heat output meaning they should provide slighlty higher mileage.

If you were running a car at Daytona flat-out most of the time, then yes, a engine detuned by knock sensors might have reduced mileage. But in everyday driving where even the most aggressive driver is at full-throttle only a tiny, tiny fraction of the time, and the knock sensors are potentially detuning the engine only a tiny, tiny faction of the time, I don't think mileage is significantly affected by running lower-octane fuel.

Having said this, I've always thought it false economy to buy a high-performance car and then feed it gas that makes it a low-performance car. If the car calls for premium and you use the full potential of the car at all, then might as well feed it the gas that makes it run to its full potential.

- Mark

Carl, your answer is only partially true. In the old days, there was no reason to use higher octane gas, unless you had a severe ping under acceleration. You are correct in that most modern cars will not ping, due to the anti-knock sensor telling the ECU of a pinging, which then causes the ECU to retard the ignition timing. The retarded timing cuts power and gas mileage. Therefore, it is likely that using a lower octane gas in a modern car that is designed for higher octane will not harm anything, but power and gas mileage will be reduced, but only if the car is driven in a manner that would cause pinging, i.e. very hot weather, hard acceleration, placing a higher than normal load on the engine such as climbing hills or towing.

In my GS 300, I use mid-grade around town where none of the above conditions exist, but I switch to premium if going on a long trip involving high speeds and mountain driving.

I have also used regular in the city and note no difference in performance or mileage, but I stick to mid-level just to have a higher margin of safety.

Steve