Does it really matter if one pumps 91 or 87 octane into thier evo? My Best friends mechanic laughed at me when i filled up the other day. The guy tells me "thats just race gas son." Is he blowin smoke up ma tail?

 

are you serious? is your best friend's mechanic a monkey? read your manual.

 

There is a reason people can get upwards of 150 hp out of tuning on race gas. Yes there is a difference, that guy shouldn't be a mechanic. I'd have for him to take out a highly tuned evo to put gas in it and fill it up with 87 then open it up to blow the motor.

 

 

Premium fuel only! it says it in the manual and the gas door!

 

That mechanic is a freakin moron. Maybe back in the day with carbs, it didn't matter as much.

Regardless, the Evo is optimzied for 93 octane, so we're already at a deficit here in Cali where we only get 91. I'll gain roughly 20whp by using 93 octane. With 91, it's already riding the knock sensor the whole way through the rpm range. I'd hate to see what it does with anything lower on the stock tune.

 

Yes it matters. Running lower octane fuels that what the car was tuned for will cause detonation or knock (detonation blows engines, especially in turbo cars). You should run the highest octane fuel that is readily available at the pump in your Evo. You should not run 87 octane in your car. It sounds like your mechanic doesnt know much about turbo cars or he's pulling your chain.

If you drive a car that was designed for 87 octane you probably won't see the benefits of 93 octane, but if you drive a car tuned for 93 octane and you put 87 in it, you could blow it up, although a stock evo will probably put up with this it's not good for the car and repeated 87 octane use could cause serious engine damage.

If your concerned with the cost difference between 93 or 91 octane and 87 octane then quite possibly the Evo was not the right car for you.

 

^ It doesn't look like he's concerned about the cost difference, it looks more like he's wondering if there's a difference between 87 an 91 octane.

 

87 is a [more pure] faster burning fuel
91 is a ["dirty" less pure ] slower burning fuel designed to reduce knock

 

u guys are lucky the evos we get are JDM Evos built to run on 100/98 octane ....here i get 90 octane!

 

thats what i figured. ive always pumped 91 octane due to having turbo cars. my first car was a 97 gst => 93 tt 300z => and now my evo. he tells me that with newer cars the ecu is so advanced to where if the car were to ping or knock the engine would automatically retard the timing to compensate. i dunno so i thought i would ask here. but thanks for the info. i fell better and will continue to use 91 WOO!

 

Only one place in the world i know with 90 octane and that would be Alaska.

I bet it would still be tunable hell i'm running 24psi spikes on 91 octane here.

 

oh, so say ive been using 93, and i acidentally put in 92, will it knock or anything??

 

possibly, but i wouldnt worry if its just once
just dont go WOT too much just to be safe

at least u have 92 octane unlike cali

 

haha i wish i had that much of a chopice. 92 is what we have here. you should be fine with 92. I have an AP for my car and i show no knocks what so ever on 92.

Also the mechanic this op is refering to must be off his rocker. I don't mean to sound like an A@# or anything but you can't make an assumption about a car like that just because its a 4 cylinder.( which Im guessing he is doing) ask him if he would put 87 octane in a Corvette.