Now that gasoline prices are well above $4/gallon for regular in many large cities, I've been wondering about using mid-grade octane gasoline instead of premium fuel in the S2000.

Has anyone tried it? Any permanent harm or damage to the car? Does the mileage suffer?

 

If I'm not mistaken, a stock S comes tuned for 91 octane but I haven't been stock for a long time. I think I'm right however.

93 octane here is premium.

fltsfshr

 

This question comes up in every automotive forum every time gas prices jump. Modern engines equipped with knock sensors (like the F20C/F22C in the S2000) adjust timing and air/fuel mixture to compensate for lower octane gas. (This adjustment does reduce engine power and efficiency.) That said, the S2000 manual says that you should always use premium except in emergencies when it is unavailable.

Using mid grade or even regular gas will probably not do any permanent harm to your engine. However it may result in lower fuel mileage since the engine is running at a lower and less efficient state of tune. So the money you save with a lower cost gas will be spent on that reduced mileage. Even if your car doesn't suffer from reduced gas mileage, 12 gallons of premium will cost less than $2.00 over the cost of 12 gallons of regular. That works out to less than a penny per mile. Wouldn't you pony up an extra penny a mile for the performance benefits of premium? (Of course premium is a waste of money in cars engineered to run on regular.)

 

All of my cars require premium fuels.
occasionally my wife will decide to put in other than the required fuel grade.
Invariably I get in and drive it and bag her every time.
You really can tell the difference in performance.

 

Here in Quebec,91 octane is considered and sold as premium.
Been running my S with that since day one,and it's running like a charm.
When I drive down to the States,I always try to use Sonoco super premium,(forgot which octane rating)and honestly,my seat of the pants,never can tell a difference.

 

Here we have 89 (mid) and 93 (premium). I go back and forth on fill ups. If I forget what I bought the last time, I default to premium.

 

And I thank you for this tip from several years ago sir - I've been doing it ever since

Thanks to my "car bible" where I track gas mileage and maintenance, I also note what grade goes in the car at the time of fill up.

 

I put about 5k miles a year on mine. At a price difference of 10 cents per gallon, I would save less than $25 a year running mid-grade. Not worth it for me.

 

Good idea, Ellen. It wouldn't kill me to carry a small notebook in the trunk with the manual.

 

Both the Vette and the Maxima are listed as needing 93 octane. When I have run mid-grade in the Maxima the mileage drops by about 10% (about 2.4 mpg). There is not a 10% delta between 93 and mid-range so we suck it up and go with the good stuff