alright.. i filled up about two weeks ago and i used the 89 octane fuel. i let that run through my system. got about 18 miles a gallon. ok not bad but when i used 87 octane and ran that, i ended up getting about 20 miles a gallon. its mostly highway driving so i drive the same way every day. and anyone answer my question???

Lots of times the engine doesn't need the higher octane fuel and it can hurt performance instead of help it.

I saw some TV report awhile back, and it said that probably less than 5% of the vehicles out on the road need anything more than low test gas.

Unless you have a chip :nuts: My dad ran super in his F350 (351 powered) for quite a while. He took back to the dealer from some warranty work on the front axle and they told him that he's wasting his money and to just run 87.

Higher octane gas burns slower. This is what you need in a higheer compression engine. In an engine designed for 87 gas the slower burn hurts performance and milage.

my 87 2.9 has been acting funny for like 3 weeks so i was running it on regular when i switched to mid weight i noticed lot more power and it running very well next thing i gotta do is get the emmisions reducer stuff and go get it inspected just my 2 cents