Should I switch from Mobil 1 0-30 to Mobil 1 0-40? Vehicle is 00 Silverado 5.3 w/54200 miles. There is some noise at start up, but I don't think its this infamous cold start knock. So far 5k interval it has used about 1/4 quart. The most the engine has used is 3/4 of a quart and that was with the 0-30 this time last year. Normally its about a 1/2 quart with Mobil 1 10-30. I am running the 0-40 in our 99 Saturn 1.9l with 45k and it seems to be slowing the comsumption compared to either the 5-30 or 10-30 Mobil 1. I was thinking of switching to the 0-40 but many on this site do not like it due to is shearing. However far more dislike the 0-30 for the same reason. The GC 0-30 is the same price at Auto Zone as the Mobil 1 0-40. Delvac 1 is not as readily available. This is my dilemma!!!