Mitsubishi Eclipse Spyder 3.8 2008. Requires 93octane booster?

If you can’t find 93 then use the 91 ethanol free (it’s better for the fuel system) and add the required amount of booster to bring the octane up to 93. I had a vehicle once that required 93 and if you tried running anything lower the mpg dropped by half. It only got 8 on premium so it dropped to 4 on regular.

Generally a high compression engine will need a high octane to prevent engine knock or pre detonation which is bad , If you can get 93 octane then go with that , if only 91 is available you may need to add octane booster . There may be an on line forum for those vehicles it's worth looking into .

An octane booster will be just fine at every fill up. I used STP Octane Booster for years in my 1970 Pontiac Catalina. The engine required premium gas but would still diesel when I shut it off. Using the octane booster at every fill up solved the problem. So it really does work. Right now it's probably cheaper than using premium too! Hope that helps! Jim

Your Spyder originated in a part of the world where 93 Octane with Ethanol was the norm for Premium gas. If you're in a place where 91 Octane is the norm, that will be fine; the engine's designed for anything over 90 Octane..... Only add a booster if you use 89 Octane or lower. Without the booster, the engine will still run, but not quite as well..... What you read is Mitsubishi's way of trying too make you think you have a real performance car.