Why is it that when I put 89 or 93 octane in my truck, it seems as though my truck is extra hungry for it and eats the **** out of it, but when I put in 87 octane I get a definite mileage increase and it doesnt burn as much?

I know the higher octanes burn cleaner, but does anyone know exactly why the 87 doesnt seem to burn as quick?

I put at least 175 miles on half a tank the past 2 days and I still have 1/4 tank left.

 

Only thing I could think of is the lead foot syndrome with burning the better gas. The better gas would make it run better, so maybe your foot's in it more????

 

not sure, I usually drive it the same, but that could be true since now I'm trying to not dog it as much.

 

Technically, it should be just the other way around since the higher octane gas will run better and let the computer give it more timing.

 

interesting

 

I've logged my fuel mileage for about two years and I haven't seen too much of a difference between octane levels. Sometimes I will get poor mileage for no good reason though, and I am not sure what to place the blame on.

My best tank was 24.2 MPG from Dallas to Houston on a 60 degree day with a good 15 mpg tailwind. I never had to turn the cruise off or adjust speed. My worst tank was 13.8 MPG. I bought gas at a Diamond Shamrock in Johnson City, Texas and drove on the highway...I was pissed at the shitty tank of fuel. This is on a 5.3L with 3.42, cat back, FIPK.