Quote:
Originally Posted by RobertISaar
you realize that when the oil is up to full temp the 0/5/10/15/20W rating is of no importance, right? that specification is for when the oil is cold, the second half of the rating is viscosity at 212*F.
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Not according to bobistheoilguy.com
For 2013 Cummins is saying that 5W30 is ok in heavy duty truck engines. I think they are coming factory filled with 10W40 instead of the usual 15W40. However, talk to anyone at a Cummins dealer and they will tell you that 5W30 is wonderful until you find your engine worn out in 2/3 the time as normal.