Horrible mpg

[JimT]

Wish I had your gears, then I could spend a little more time in top gear.

It took me a lot of testing to fine 1400-1600 to be my best economy range. Actually, 1350 rpm in top gear (63mph) on cruise used to give me 8-8.5mpg all the time. BUT that was before I learned that below 1400 wasn't good for the liners at higher loads. When I first got the truck I learned pretty early that anything below 1250-1300 under a load just didn't feel right from the engine. But now that I know better I try to keep the rpm's higher and the boost lower. Took a fair bit of work and tweaking to get higher mpg with the higher rpms and lower boost. I didn't mention it before, but I know my CAC has a leak near one of the mounting points. The thing is, when running with the least amount of boost possible you don't notice the loss like you would when trying to make higher boost. At least that's what the numbers look like to me. Like running I-84 east bound through NY just past the Newburg-Beacon bridge. I can climb that grade by the Stormville rest area with 15 psi boost, I just end up moving about 25-30mph for a minute or two.

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Do you have Insite? What does your regen history look like? You could be losing some of your fuel mileage to more frequent regens or regens that are struggling to complete properly. When was the last time you did a full EGR tuneup? (not just replacing sensors)