I’m new here and I have some questions.

[Waterloo]

(01-14-2020 )cowboycurtis Wrote:  

(01-14-2020 )Waterloo Wrote:  As far as your fuel mileage, that is going to be up to the driver, first thing you do is slow down, best fuel economy is going to be around that 60 to 63 mph at 1700 or so rpm's. I have an 18 speed in my truck and run her on the highway between high 7 and low 8. I rarely go to high 8.

Wow. That surprises me. Mine is also an 18 speed and just assumed that lower rpms were better if the engine wasn’t completely bogged down. I figured if it could gain speed from around 1400 that would be a good spot to let er run. Crazy thing is I can get 7-7.5 mpg in those Detroit’s no matter how hard I push em.

Fuel is expensive but so is time. I’ll sacrifice a little fuel to save some time. Trucking is a secondary job to my farming and seed operations.

NO NO NO! If you run these ISX motors at those rpm's you will bust a liner lose! Usually the #5, it is a design flaw from Cummins. These motors need to be kept above 1400 rpm, I try to keep mine above 1500 rpm's. I run her right up to 1800 or 1900 to complete the shifts, you will not hurt the motor running that high.

What gearing do you have in that truck?