Gearing / Tires and Fuel MPG?

Fist question is what do yo want to do? OTR.? Regional?
Flat? Dry? ......North? South? East coast? West of Rockies? I need more info to help you.

 

First off; forget about the Mack. Mack motors are not known for fuel mileage. Secondly, it is more difficultto find parts and service for a Mack when you are on the road.

You should be looking at Pete 387's, KW T2000 and T600, or frieghtliner Centuries or Columbias.

Detroits are usually the best motor for fuel mileage, although a cummins does a good job as well in that department.

As for spec'ing the truck; the most important thing that I need to know is; how fast do you plan to cruise? You need to decide that first, then spec the truck so that it runs as efficiently as possible at that speed.

 

Like has been said you have to spec it for your driving style and speed. If you are going to run out west where its 75 mph speed limits spec it to run in the sweet spot of the motor in high gear. and the Detroit is going to be your better eng for that. Now as to trans i like a 13 double over but thats me every one to there own taste. Some like the 18 some like the 10 if your going to be in the mountains you want a trans that is going to let you keep it pulling. Now as to the tires highway non lug will get you better fuel millage but you loose the traction that is required in bad weather so its a pro con thing i always ran lug tires on drives and averaged over 1.4 million miles on a truck with about 5.8 miles to the gallon on a fld 120 with a 430-470 Detroit and 13 speed with 3.73 rears i missed the gears when i ordered it the speeds were at 65 and then they jumped so i missed the sweet spot should have been 3.55 or so and it would have been better and could have jumped it to 6.2 or so. Now horse power and fuel millage are not going to change unless you get to little horse power so get as much as you can just cause you have doesn't mean you have to use it. A 550 or 600 horse motor will get as good if not better millage than a 400 or 450 motor if driven right. The driver has as much to do with fuel millage as the equipment and gearing has the most to do with fuel millage. Ok thats my take and my feelings on the subject and as far as which truck and model as long as you stay away from the square hoods you will be fine on the aero side now me i will sacrifice a little fuel millage for the hood but thats just me and my taste.

 

5.8-6.2 was respectable fuel mileage back in the day. Now that type of fuel mileage will put you into posting in the threads calling for strikes and government intervention. You need to spec a truck and drive it in such a way as to average 7.5 mpg if you want to make a good living in the current financial enviroment in this industry.