In California, we can buy only, 87. 89 & 91 octane. What if save $.10 / gallon and put in 89 instead of 91? I thought I read in the manual that while 91 is recommended the computer will adjust to 89. What if any harm is done?

 

since this is a high compression motor, you have an increased risk of pre-detonation with lower octane. I believe the computer will retard spark timing to try to compensate, but then you're giving up horsepower.

you bought an S2000. it's a sportscar. give it sportscar fuel and don't worry about $.10 here and there.

 

what a cheap skate.

 

^ ...the car will start tikcing and whatnot wont it?

 

Nothing bad will happen, except you lose horsepower, unless you consider that bad, which then something bad did happen. If you put lower octane gas in, the computer does retard spark timing, and you lose horsepower. Does it hurt the car? No. You just don't get the advertised 240 hp at the crank.

 

I agree with the last one. As far as i know the car is "mapped" to a octane. It means that it could behave a bit different if you go up or down on the octane level. I tried an octane level of 99 her inn Norway (Shell formula one 99 Octane). Just for fun really, as it should give more power. But again if the engine is not mapped for it, it might not give the right response. Never heard that the computer can self adjust? if it does that is good. But eg. I know that Rally cars drive on a racingfuel that has a very high octan and they have to be mapped for that stuff. It cant run on "normal" fuel.

 

91 only. please

 

It might run OK on the retarded spark, but if the knock sensor fails, doesn't 'hear' the knock, or something happens, you'll damage your motor.
If you're going to run 89, don't push the car. Just cruise around and don't push the car.
Is it worth saving 10cents? I don't think so. And clearly you don't have the money to rebuild the engine if it fails....

 

$.10 per gallon
12 gallon tank
$1.20 per fill up

The look on your face when you develop engine knock to save a buck or two a week? Priceless

 

^ +1

If you can't afford the $50 or so extra gas costs over the course of an entire year, you probably shouldnt be driving a sports car.