hey i have a 91 150 300 L6 with 3.08 gears. thinking of putting 31's under it. does anyone have any experience with the mpg changes? how much should i expect to lose?

 

I get about 16 high way on a good day.

 

The 31s shouldn't hurt your fuel economy very much. They didn't really effect mine. If they did it was 1 mpg. Something else to consider is that your speedometer will be off a little bit, so to get accurate MPG figures you need to setup it up for 31s by changing the speedo gear which is pretty cheap and easy to do.