"Not sure of the "marketing verification"...marketing to me means advertising. Even if the Mobil 1 is not the ultimate oil it has been validated under the worst case product testing for that specific product...that is not just "marketing". Besides, as I have said, someone has to test it...we test the Mobil 1 and recommend it as good. If you want to use something else....YOU are doing the testing. If this irritates you that GM does not test all the other alternatives understand that we also do not test all the other tires, spark plug wires, spark plugs, etc.....we provide a validated product and provide the specs to maintain it as validated. If you think that you can do better, have at it...just accept the responsibility if you don't. When you are developing an engine there are many many things to do and investigate. Some things you take for granted if they are working and use them I suppose. GM has definitely had a good working relationship with Mobil over the years. I would say that it is a mutual relationship as they see a lot of engine tests with their products and we get their undivided attention anytime there is the faintest hint of a lube related failure or question. They make a good product."