Hi!!! With the heat the turbo motor puts out, I have been a quart low after about 1500-2000 miles, normal right? I wanted a heavier oil and didnt want something as heavy as 20w-50 so I tried Rotella 15w-40 last oil change. I never had to refill as there was no burning off, now that its 5000 miles later, was wondering if I should do another oil change with the Rotella. The engine ran nice and smooth with it with no power loss. I know I dont need the soot protection this oil has, but is there any negative effects of 15w-40 diesel oil?