Highway MPG with a 3500 Dually

[OuachitaAdventure]

Took my truck on a road trip today and did some hand calculated MPG test. Average speeds of a 70-75 I got around 17.1 hand calculated.

 

[Deleted member 80]

That's a solid 2-3+ mpg better than I have seen with my dually HO, Aisin, 4.10, even if I keep the speeds down some.

 

[OuachitaAdventure]

4.10s probably make all the difference there

 

[Deleted member 80]

4.10s probably make all the difference there

While they don't help, it's only a couple hundred RPM difference, and when I have watched the instant MPG with the cruise on it actually trends up a bit as I bump 1+ mph at a time starting from 65 mph. There seems to be a much greater difference between the new HO/Aisin versus the Std/68RFE than in prior generations.

 

[OuachitaAdventure]

hmm, that's interesting. I guess you need more fuel for that extra power...

 

[Deleted member 80]

hmm, that's interesting. I guess you need more fuel for that extra power...

What's odd is my truck doesn't take any more horsepower to go down the road at any given speed, RPM difference aside, than yours. I think their lower compression, higher boost strategy to acheive big numbers under load are impairing its ability to cruise efficiently at low loads, if that makes sense. My old Cummins would really make good MPGs on rural roads where you were travelling just fast enough to stay in top gear without excessive lugging. This engine does particularly poorly in those circumstances, judging by the instant MPG.

 

[DevilDodge]

I have to agree. The main reason you do not see the HO Cummins in the 2500 is because it isn't designed to be a multi tasker. So, your observation is correct as it is designed to work, not one other thing.

 

[OuachitaAdventure]

I have to agree. The main reason you do not see the HO Cummins in the 2500 is because it isn't designed to be a multi tasker. So, your observation is correct as it is designed to work, not one other thing.

So maybe the Non HO version is better for the occasional tower if MPGs are a concern.

 

[Deleted member 80]

So maybe the Non HO version is better for the occasional tower if MPGs are a concern.

That seems to be the case.

 

[DevilDodge]

Yes, that is what I was saying. The HO is for working, the non HO will better suit a truck that spends more time as a people hauler vs a full payload or a high GCWR