Have you been idling the truck at all?
Ive had three cummins diesel trucks. A trick .I read on the cummins diesel forum is put a drop of your oil on a kleenex. If there is diesel fuel in the oil it will spread out from the drop over time. You will end up with the black oil drop in the center surrounded by a yellowish/brown area around it. I tried it. There was no spread from the drop. Oil analysis confirmed this. The guy that posted showed a pic of the drop with the surrounding yellow/brown area. Oil analysis confirmed he has diesel fuel in his oil.Here's the issue, I've checked the oil a few times since I bought the truck in early September. The trend seems to be an increase in volume, with out being overly dirty or strong diesel odor. I've checked about every 1000 miles, with about an eighth of an inch increase each time. When I parked it in the driveway on "day zero" I verified that the fluid level was correct, so that's not it.
So now I'm at a level that has become concerning, real close to 3/8 of an inch over the full indicator on the dipstick. I've checked it in the same spot each time and two different locations on level ground today to confirm the readings. I haven't had any CEL's or Indicated Regen's and have been getting super cool fuel mileage (29.5+ MPG). I drive mostly country roads (50-55 mph) with some town driving kids to football, wrestling, basketball and all that good stuff. Done a few trips to the beach and hauled some firewood and such, but now good tow's yet to really build some prolonged oil temps above 217F or so. I usually run around 208-212F on the average around here.
I'm not a big diesel guy, but no big dummy either, so; any other folks finding the same issue under the same conditions, or even heavy use? Does anybody have any recommendations? $.02?
Out here in the Great Northwest, it's been really warm, barely been below 50F, for what it's worth. Thanks.