This is very good oil for GM diesels. The current engine has a crankshaft relate noise at normal operating temp (NOT), I believe due to an inferior oil pump design. Below 31PSI, a crankshaft related noise is discernable. I have written GM on possible solutions that are cheaper than replacing the engine under warranty. The 20W50 helps keep the oil pressure above 32PSI at idle which stops the noise. In the colder months I have cut the oil 50/50 with 15W40 DME, but once at NOT, the crankshaft noise does come back. This engine seems to need 30W oil to prevent the noise at NOT at idle. I am unable to find a good 30W diesel oil with API CI-4 or CK-4. The 20W50 from AMSOIL is the best at helping this situation until they make a 30W or 30W40 for this engine.

The product is great and I have ordered many times. My last order arrived with a punctured leaking container. Tried to contact Amsoil with photos but received NO response. Could do much better with customer service.

Great oil, not only for competition motors. You can hear and feel a difference in the engine and idle.

I use this in my 2019 NPRHD Box Truck. It provides exceptional protection compared to Mobil 1

Excellent quality oil. I would not be afraid to say " state of the art ".

The motor oil ran awesome but I’ve been waiting on my last order for 2 months and it’s still a no show... unimpressed with my shipping experience but this oil is gold!