I have a 2005 mustang GT with a C&L Racer and im running a 93 octane tune, but today my dad took my car and I believe he put a little over a quarter of a tank of 89 octane in my tank. I've only drove it probably 4 miles with the 89 in my tank. So what should I do? Should I change the tune to the 87, or just leave it the way it is and let it run the tank to empty?


Thanks

 

I would change to your 87 tune immediately and then run it down and fill up with 93 before you change back to your 93 tune..

 

You might be able to just retard the spark and still be okay.
If you load the 87 nothing will be damaged for sure.

 

If he put a quarter tank of 89 in along with 3/4 tank of 93, your overall octane rating will be 92. Just retard the global spark by 1 degree, you'll be fine. Once you fill up the tank again with 93, put the spark back to normal.

 

Just drop back to the 87 to be safe

 

There really is no need to worry or do anything. As long as you do not hammer the throttle and you do drive very conservatively until the gas gets low enough to then re fill you will be fine. But you must drive like a little old lady.

Richard.

 

I have a question about this subject. My 05 is stock right now and I run regular and every couple of months I run a tank of premium just to kind of "clean things out". When I install the JLT CAI & 87 tune, will I have to change to the 93 tune if I want to do the same or can I run a tank of 93 on the 87 tune?

 

you can run a hight octane gas on a lower oct tune, but you will not get the benefits out of using the higher oct gas without a supported tune.

But if you do it the other way around with a higher tune and lower oct the fuel will ignite at the wrong time and you most likely would hurt the engine. This is only if you are running hard. if you drive like a granny it should be ok.

 

+1. You also won't get any cleaning benefit from running higher octane gas. It isn't "better" gas. It just resists detonation better.

 

That's what I kind of thought but I just wanted to make sure. I knew doing it the other way around would be harsh. Just to be on the safe side maybe I'll change the tune when I do run the premium. Thanks alot by the way!

 

Running premium fuel as a cleaner is useless and in fact if the car is not tuned for it you will essentially be pushing unburned fuel right out the tailpipe. If you use a top tier fuel you do not have to worry about running fuel cleaners or additives for cleaning as they are already in the fuel.

http://www.toptiergas.com/index.html