Help with Fuel Mileage

Different final ratio on trans could reason. Just my 2 pennies.

 

3.70 will do that. Look into 3.42 or lower. I personally have 2.93, a bit of a struggle up hill with 13s but great on mpg under heavy loads.

 

Dont forget to slide the red bottton forward:smt064

 

Where are you keeping RPM's at roadspeed?

 

3.70 rears will get you up a hill, but 3.36 will get you better fuel mileage. I guarantee your final drive ratios were different between the 10 and 13.
With my 2000 WS 12.7 13A and 3.36 rears, I get 6.5 all day long light and better if it's low profile. On my recent trip to Seattle, I averaged 6.6 and that was 4,000 lbs but the piece 10'2" tall and tarped. I've got 10 foot tarped now coming back at 41,000 and not nearly as neatly tarped, so I hope to have tailwinds and get 6mpg through MT and SD.

 

Withit......I've got the same setup as u, except for a DDEC V. Your rpms/ mph is a lil high for optimal mpg's. I run @ 1300/ 58mph and I get anywhere from 5.5-6.4 depending on conditions, terrain and load (I flatbed). Rollin slow ain't for everybody, but money in the bank usually is......

 

With my setup above, I'm at 1350 @65, and 1500 @ 75.

 

with ddl 6.4 you can chance the parameter this is easy just chance final ratio to .74 and set your injectors to 75 and ready