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tunning and gas


Well-Known Member
with gas pricese the way they are i was wondering if your tuned for a 91 oct could you use 87 oct and still be ok or do i have to go spend money to get a seperate tune to run 87 in my car. thanks for the help yall



Crew Chief
Staff member
Board Member
If the car is tuned with 91 octane, then you need to use the 91. You will have pinging (detenation when not wanted) in the cylinders when you get into the throttle hard or if your traveling up any hills.


Well-Known Member
Well, with today's engines and pcm's.. you can throw 87 in the car, but being tuned for 91, the pcm will have to take out some timing in order to keep from pinging.

And that's saying whom every tuned your car has left your knock sensors on, or has not adjusted there sensitivity to where your pcm cant see and then make changes for your 87.

Who every did do your tune should be able to pull some timing from the tune, 2* per 1 octane is a good starting point. Short answer is you can run 87 octane, and the pcm should save the engine from pinging..but why trust it, it will be down on power and the safety net is not there. If you want to run 87, get a tune for 87...it will run allot better than if the pcm detects knock and pulls timing like that.