Originally posted by bensenvill:
so the SVT is set for premium... I didnt know that.
I can say that when I use premium, my mpg drops a tad [but it feels like the car has a bit more giddyup].
Not that I am an expert on this, but maybe your cars running really rich on premium and the lower octane is running a bit more efficient.


You're right. You're not an expert.

Also your Cougar is programmed to run on regular so of course efficiency would drop with premium.


Also any one just randomly changing octane is going to have erratic results. The PCM is adaptive but it's not an "instant" change. It is a learned altering to the new setting/variable/change and it takes time. If you keep changing fuel and yes this can even mean different gas stations (i.e. brands of fuel blend) it will never run at optimum efficiency.

Trying something just once is NOT trying it. It's just being foolish really. If you really wanted to "test" a change you would reset the PCM after you filled up and drive several tanks on the same fuel to get any results worth mentioning.

My highly opinionated 2 cents on this commonly misunderstood topic.

2000 SVT #674 13.47 @ 102 - All Motor! It was not broke; Yet I fixed it anyway.