Pablo wrote:
The engine manufacturer-- VM-- states they do not recommend anything above 5w as this engine is so tight it has negative clearances at startup. VM knows that most are never going to do a turbo cool-down before shutting off the engine, as well. This is another reason for the synthetic only requirement. You could hardly blame DC for voiding your warranty if you use a 15w non-synthetic instead of the 0w or 5w synthetic (especially in cold climates).
The reason most big operators use the non-synthetic 15w-40 instead of a synthetic is not because its the best protection, but rather because it is the best value. Its cheaper than full-synthetic's and good enough when used by people who know the procedures for operating their vehicle and who get the fluids changed on time. No operator wants to spend the money to buy synthetic when you needs gallons of it to do a single change, its just too cost prohibitive. At only 6.4 quarts-- it is not so bad for us. Also consider that you don't drive like a big rig-- which starts and then spends forever and a day in its operating temperature range. You may have lots of stop and go driving where the engine spends much longer getting into temperature range and goes through many more thermal cycles (shut downs). All of this would argue for synthetics.
Probably closer to the truth that DCX expects this engine to ingest & pass unreasonable amounts of oil thus a more stable synthetic is less likely to coke the VGT and EGR hardware.
I can understand using a synthetic but CF-rated oil (0W40) just doesn't make sense in this application. Detroit Diesel has been anal about requiring a CI-4 rated oil with an EGR engine and will void a bus engine warranty if not used (mixing oil grades is a known problem in bus fleets so DDC will ask for an oil sample if a warranty claim is filed). BTW, in Europe the standard turbo-diesel oil formula for this engine is a 10W40.