i have an SCT2 tuner and i havn't installed it yet. but i am going to tune the car for 91 octane fuel, is it bad if i do it when i have almost a full tank of 87 octane still left in it?

 

Just my opinion but (I think I am right) to get the full power from the tune you should wait to get the higher octane fuel in there. With the lower octane fuel you risk detonation if you get on it hard and if you can't get on it why retune?

 

Ben's definitely right, you cant run a higher-octane tune with low octane gas or you're engine will be pinging.

 

ok since here in south texas we have 89 octane instead of 91 will that be a problem or should i play it safe and program for 91 and use 93...or just through it out the window and reprogram for 93

 

Run a tank of 93, and then retune for 93.

 

What I would do is run it on 87 till almost empty, then fill with 91. After that tank is gone upload the 91 tune.

 

I would play it safe, and program for 91 and use 93 oct fuel..And would not program for 93 until at least, running a couple of tank full's of 93, just to be certain that any remaining 89 oct. fuel, is completely out of you're system..

 

Yes, that's exactly what you need to do, and just to make certain that you have no remaining 87 left..I would actually run 2 tanks of 91 or 93, before uploading the 91 oct. tune..which was exactly, what I did..Better to play it safe, than run the risk of causing detonation problems, which could end up, burning you're pistons..

 

well since no one else said this, i would just get some octane booster if you still have some 87 etc. You can buy like 104 octane boost cans around here in st. louis. So by adding the boost you should come out ok. Good luck either way.

 

I know too many people who ruined their plugs, etc. to ever consider dumping an octane booster in my car.

 

In my tuners words. "All you have to do run the tank close to empty and fill up with 93 and then go ahead and load up the tune. You will at least be at 92.5 and that is close enough."

You do have to run the engine or drive a bit just to get the 87 that is already pumped in the fuel lines pass the injectors.

There is no 87 floating around by itself somewhere.