OK i know someone is gonna get all upset that im asking about mpg's. I have done some searching but everyone else has bigger tires are smaller motor or what ever, so i feel this is different.

OK so i have the 5.9 with 275/70/17, 4.10 and do almost all city driving about 8 miles a day, I never really paid much attention to mpg because i had larger tires and so my speedo and odo was incorrect. I recently downgraded and was able to check mpg, I am only getting 8.3, 8.5 or so on two fill ups. This seems a lil low, i know im gonna get the "these are big ol truck that love gas" and "if you want better mpg, get a honda", but arent those mpg numbers kinda crappy? Oh and everything is stock.

 

well you do have 4.10's so with stock size tires that will hurt your mileage in the highway(i know it lowered mine as i just went from 3.55 to 4.10). However since you do most driving in the city i dont know how 4.10 would affect mileage. As mentioned in almost every other gas mileage thread have you done a tune-up. Spark plugs, rotor and such.

 

how many miles on your o2? just replaced mine and mpg went up a little.

 

He also went down in tire size which with 4.10s will affect the MPG

 

No haven't done plugs wires etc, that's on my to do list. Does plenum, cat, o2 all affect mpg?
o2 probably stock.
Does going down in tire size negatively affect mpg?