D'prived

I purchased an SCT tuner with the 3 tunes (87, 89, 92) along with a Ford Racing CAI from American Muscle about a week ago. I uploaded the 87 tune because that's what I had in the tank at the time.

My question is this... If I pull into a gas station with, let's say, one gallon of 87 octane left in the tank and I fill it up with 92 octane. I am now running an 87 octane tune with 92 octane in the tank. Is that going to screw something up? Do I have to bring the tuner with me and upload the 92 octane tune at the gas station? I'm a little confused.... help me out please...

alkemist

If you run higher octane gas with a lower octane tune, it will not affect anything. Now if you run a higher octane tune with lower octane gas, then there is chance of detonation.

D'prived

Thanks for the input Alkemist. I guess bottom line though wouldn't it be best if I brought my tuner with me, filled up with 92 then pull off to the side somewhere and re-tune with the 92 tune?

alkemist

Some people prefer to run a tank or two of the next octane before switching tunes. Personal preference. I would leave as little of the previous octane (87) in the tank as possible. Don't forget that the s197 has a 16g tank and 1g is kept in reserve. So that would leave you with 2 gallons of 87. From what I recall, I ran a full 93 before I switched from 87 to 93.

D'prived

Great! Thanks for the info. I really appreciate it! I'm going to do that.

alkemist

Sure, no problem. Have fun with your tunes

FastDEW

I agree. It is best to run at least a full tank of 92 through before installing the tune. It may not really matter, but if you get detonation it isn't a good thing.

When I installed my tune I already had the 91 octane in from day 1 so I just uploaded the new tune. Having said that, I did actually load the tune while I was gassing up at the pump. It only takes a few minutes at most to upload the new tune. Not long at all.

JIM5.0

As an alternative, you can drain the gas tank and fuel up fresh with all 93 octane. That way, you are guaranteed to not have any diluted fuel of two octane counts mixed together.

D'prived

Oh yeah... that sounds easy enough!

BruceH

You can also run your tank down and put in about 2 gallons of 92. Run it down again and put in 2 gallons of 92. Then fill up and change tunes.