I was running a brenspeed 87 octane tune and liked it. Over the weekend I decided to try the 93 octane tune.. drove it to empty and filled it with Shell 93 octane.

I like the 87 octane tune better. With the 93 tune the car seems to hesitate a little (throttle lag) when I step on it.. and knocks occasionally.

I still have 3/4th tank of 93 in my car.. is there any danger in switching to the 87 tune with 93 octane in the car.. or do i have to wait a week or so before the tank is empty?

I've heard of people running 89 octane with an 87 octane tune..

 

Just leave the 93 in until you are done with the tank unless the knocking is constant.

 

i've heard u can mix 91 with 93 or vise versa but when u run 87 it isn't good to mix with the highest octane

 

There should be no problems stepping down the tune while having higher octane gas in there. You run into trouble when you "starve" the engine of the octane it thinks it needs. Realistically there shouldn't be a problem with filling it up with the 93 but it can't hurt to wait untill you're almost empty before putting a new octane in there.

 

gotcha. Thanks.

 

There's a good chance that you had more 87 in your tank than you thought, and adding 93 to that might have deluted it see if you can hold on with the 93 tune and keep filling up with 93, that should cure the problem.

 

I would wait until I have a 1/4 tank then fill up... your stang should be fine

 

You can run 93 octane gas on an 87 octanetune, but youshould notrun an 87 octanegas with93 octane tune, not hard anyway.The octane you runshould be at your level oftune or higher or you riskpredetonation.In an emerency you can run an octane lower than your tune, just don't run it hard. You might want to finish off that tank of 93gas before you decide to step your tune down. After you run a tank or two the predetonation should go away. I am running a Steeda CAI with a 91 octane tune with no predetonation.

dseid2

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I ran my car down to1/4 tank then filled up with 93, ran it down to a half tank then filled back up with 93 down loaded my B a m a chips 93 performance tune with no problems, car runs great.

 

Like mentioned, you can run a 87 tune with 93 octane, could be some hesitation since 93 is harder to ignite than 87, but will be fine. The other way around wouldn't be good since you have some knocking with the 93 and 93 tune. I've used the 87, 91, 93 tune with the right gas and no problems. They might have bumped to much timing for your 93 tune or you car doesn't like that much timing. You could go into your programmer and bump down the timing about 2% through the rpm band and see how it feels or run your 89/91 tune with the 93 octane and see how it goes. Also i have my tune set to 91 but use a mix of 89 and 93 octane with no problems at all.