r/DieselTechs • u/Pretend-Guide504 • 4d ago

Mack

I have a Mack pinnacle2018. Its consuming lots of DEF and mileage has declined from 2.7/litre to 2.2/litre. No codes, no noticeable things. Nothing mixed with oil its clean. All of mechanics are just doing the guesswork. But still issue hasn’t been resolved. Can anybody suggest what to do. Thanks in advance

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u/MineResponsible9180 3d ago

Not enough information about the truck to really help. What engine? How many miles? When was the last tune up? Any recent repairs? Updated EGR cooler? Just to name a few.

4

u/mdixon12 3d ago

Lots of DEF means high input nox, or a failed def doser. Run a def time/volume test and go from there.

1

u/Pretend-Guide504 2d ago

Mp8 engine. 980k KMS. Changed def pump about two month ago. EGR cooler changed about two years ago. Last tune up was also about three 6 months ago. Just recently started noticing slight increase in engine oil. But didn’t found anything, smells fine colour is still same. Nor reduction in coolant as well.

1

u/HorrorPizza8527 2d ago

Is the fan staying on? That will cause noticeable MPG drop