Originally posted by CueballSVT:
Originally posted by DemonSVT:
All you folks ARGUING and DEFENDING the low octane in an SVT point are MISSING the BIG POINT.

Running lower octane then the PCM is programmed for will significantly LOWER GAS MILEAGE!!!

So now you are getting less miles per tank. So much for saving that extra money because you now need to fill up more often.




Actually, my experience has been that my miles per gallon IMPROVES on 89 octane. Some of my highest miles between fill ups have been with 89. By the way, I average 24-26 mpg in mostly highway driving.


Was that a one tank occurance or tracking average mileage over a 1000 miles or more though verses 1000+ miles of the exact same driving style and type???


With lower octane fuel the SVT engine is running at a lower efficiency. (significant timing retard!)
Lower efficiency means less power & less mileage. It is as simple as that in layman's terms.

If you want me to figure out exact losses you'll have to wait for me to dig out my old text books.


My modified 2.5L averaged ~24mpg in mixed driving with my lead foot and redline almost every shift. Running 92 octane Amoco and normally with some type of octane booster.

Even the 3L is averaging about 21-22mpg so far and the large majority of that mileage was both winter (which lowers mpg) and testing (which KILLS mpg!)

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