Delvac or Rotella?

You could well be right, that it's more likely something else. But I'm taking the OP's word when he says" "Nothings really changed variable wise. Not getting horrendous head winds, same loads running yoplait dedicated, still going 55mph, and weather is considerably nicer." I think he addressed the obvious, but you make a good point re: the charge air system. A leak there and the fuel mileage is toast. That's certainly another possibility and not that easy to detect w/o statically pressurizing the system..

 

29xxx trailers with a mish-mash of retreads and worn-out drive tires. 100xxx trailers with wide singles and worn-out drive wide singles... both abused to the max by inexperienced drivers curbing tires, too many tight turns. Compare that to brand new trailers with deployed trailer tails that will get you 0.5mpg increase right there. These guys most likely don't pull the same trailers more than a few days, plus the tendency to not balance the loads... that can be worth another 0.5 mpg, especially on a tail-heavy load.

There's a lot of things that change in that operation... even though it's the same curdled milk gettin' pulled around, LOL!

 

That works. If you go to the parts counter at a Prime shop and ask for oil they give you Delvac.

 

We dont seem to.have alot of say on how the freights loaded, so aside from single double single, or double double all the way back, whats your suggestion on balancing the load? And if your in a light weight, forget about being able to balance the drives and tandems, youre almost always going to be dragging the load. Its harder to get mpgs out of these then the condos in the hills, but boy do they shine on the flat ground. Im pulling a 6.7avg in hills, but better then 9 most times in decent terrains. Thats with 42k in the box

Delvac is good stuff, no worries there. if there's any contamination in fuel side or junk filters I could definitely see a 1mpg dif. And its 15w40 for the dd series engines

 

Most of the big differences you guys see are on account of the tires on the trailers. Ever since that jerk that runs the maintenance side started putting worn-down drives on the trailers, you'll see big differences in fuel economy. Go from a newer trailer with wide-singles to an old trailer- duals, mish-mash of retreads and open-shoulder drive tires, and you'll see that mpg difference. Add a tail-end heavy trailer, and it could go to 1.5 mpg. I was getting 8.9 yesterday with a 110xxx since Saturday morning. One day... not even that... 300 miles with 28888 and 4 nearly new XDN-2's (rolling resistance around 145) 2 XDAs worn down (RR about 110) and two trailer tires... I'm down to 8.4.

Rotella vs Delvac won't make a difference, but 10w40 vs 5w40 full synthetic will net you about a 2% improvement no matter whose product you use.

 

I have a dd15 with Mobil delvac Oil in it it is using gallon of oil every 3800 miles does anybody know why. Miles on it is 330000

 

They didn't ask if you wanted Delo? (Not same as delvac)