Right now I am running 31.5 x 10.5 Goodyear wranglers on my 83 CJ7. I was wondering what 33.5 x 12.5's would do to my fuel mileage. It's a daily driver with some off-road use, no rocks to crawl down here in Florida. I recently installed the Howell TBI and am getting roughly 12mpg city, and 15mpg highway. Just curious.
Keep in mind, (some how this never seems to be mentioned when this subject
comes up) that increasing the tire size (taller over all final drive ratio) increases
the size of the error in the speedometer AND the odometer, so your MPG
calculation is also effected.
Of course, if you've re-geared or replacled the speedo drive gear in the T/C
to compensate for the larger tires then this is a non issue.