I have 3.55's, in town I get 15-16mpg empty, but on the freeway Im breaking 22mpg empty. I wish my town driving was better, but realistically, its 4mpg better than my 1/2ton gas rig ever got! So Im happy

Diesel Trucks are Great on the Highway
 

I run bigger than stock tires on both trucks. 3.73s in the '07 and 4.10s with a Gear Vendor in the '91. So both my trucks are geared for the highway because that's where most of my driving is. If it wasn't, I'd be driving something else.

Id like to have a Gear Vendors just for the fun of it, but theyre slightly expensive

I have 3.55 on a 2wd and am getting a little over 19mpg around town, haven't had it on a road trip yet, so don't know highway mileage. Tires are 245 75 16, considering 265 75 16 next time I need them. Is yours running smoothly? Is the air cleaner good? Dragging a brake?

i can get better mpgs out of 3.55 than 4.10 with a empty truck. heavy towing and tire size will play into mpg too.

i'm running 305s, with 3.55 gearing, roughly 50/50 split between highway and city driving, 150 hp sticks and a tst box, I'm averaging right around 19.3 currently, hand calculated, not corrected for tire size.

Thats not bad at all dukeboy. Found a set of 3.27's to replace my 3.55's, Im shooting for 30mpg highway :yeah:

I wish I hat 3.73's for around town, I get poor mileage unless Im going over 50.. The constant getting up to speed is killing me with these 3.55's