Mileage experiences with 305's (are my calcs right?)
 

The Mileage is killing me in my 06 5.9 automatic. Currently at 6100 miles and my best tank has been 13.6 hand calculated.

Some other info: I have BFG 305's with the speedo adjusted to 285's (max the dealer could do). Are my calculations off? Do the 305's diminish gas mileage that much? What are you guys with 305's getting?

Thanks in advance,
Tbone

thats rough. get a smarty so the speedo will read accurate...the milage will go up eventually. i think i get 13.6 while towing my boat. that would make me sad

brett

I believe the BFG 305/65 are the same height as the 285/70 tires, and are about 1 inch wider. I have the 305's, but have a 6speed and the XZT helps a lot too, and I am getting about 19mpg.

What gear ratio are yo running?

I think 3.73's. 6.5k on the odometer. Got 367 miles on the last tank which averages about 12.3mpg with mixed driving. Can I expect it to get that much better? I'm afraid to see what I'm going to get towing.

this hurts

That sounds about right to me. I got terrible mileage the first 10k miles and it slowly creeped up from there. Right now at 43k my overhead is reading about 18.7 but my hand calculations are around 16.5 w/ 70% city.

Some hope here! Just drove down to Houston and back on a tank of gas. 75 mph @ 2k rpm netted me 17.95 mpg hand calculated.

My speedo is calibrated for 285's so I am guessing the mpg's are still a little off..

My speedo is bang on with the 305's at the 265 (31.4" = factory) setting, gps and radar verified...you calc's might be off a bit.