2012 Volvo/Cummins ISX 485hp 5.5 fuel mileage

Check Rawze.com

 

Chinese tires would not drop mileage that much. Check Rawze like the guy above said

 

I have an opinion on this matter.
3.55 rear end & 18 speed.
Going through all those gears your blowing fuel. The 3.55 probably a tad high. I ran a 3.42 with a 10 speed got 6.2 to 6.5 with no APU idling a lot.

 

I have 3.42 in my Volvo with 13 speed and I consistently get 7.5 to high 7's

 

Never got too much into the 7s. I could get 7, low 7's. I did better with the Cascadia. That was almost always heavy and always averaged 7 plus, but had an APU as well, no idle. But almost always heavy. Volvo was 2/3 time heavy. The Cascadia was driven faster overall too I think.

 

62,000 GVW would be heavy for me. I average between 50-55,000

 

I average 6.3 - 6.7 with d13 18spd 3.08 rear ends but i run the speed limits. As others said check rawze