Well, since this is my first post I figger it might as well be a good one. Please feel free to flame me for lack of white paper to prove that statement. But hey, take your best shot. I just bought a New Silverado with the 5.3 and AFM and I don't know what factory fill was...you don't either if you didn't put it in there so I drained it and put my Mobil 1 5W-30 Truck and Suv in that I have been running problem free for several years since before the Extended Mileage stuff came around. Slightly off topic...those 5.3 AFM V-8 engines are super simple and they work great...I do have a 6 speed auto which I think makes it overall a better package than the old 4 speed...but that's another thread except the cold start tick at start up. You guys with the 6.2 Corvettes might give this a try too since this seems to be a common complaint. I did notice the Mobil 1 has GM6094M where as Castrol Edge has both Gm6094M AND GM4718M. Ok...so my new truck has no cold start up tick with factory fill oil...I changed it at about 800 miles to the Mobil 1 truck and Suv with Mobil 1 filter and after say 3000 miles it would tick every time cold and later got to where it would tick sometimes even when already warm...LOUD but only for a second or 2. I saw a deal on the Castrol Edge at Wal Mart ($26 5 QT bottle) and figgered I had nothing to lose...stayed with the Mobil 1 filter just for grins as a test control factor. HERE WE GO>>> After about 800 miles on this oil no more tick cold at start up, none at warm start up and the valve train itself is a touch quieter overall now with about 4000 miles on this current oil. As far as I'm concerned it's a freakin miracle. I do Extended drain intervals which is consistent with the OLM...I was so concerned about the Mobil oil I didn't wait. I'm glad I didn't. Isn't it just a touch coincidental that my issue was lifter tick using Mobile 1 and Castrol targeted the issue in their test to claim 8X better or whatever and then I start using it and the tick goes away? Kinda makes ya go hummmmmmm don't it? If anyone is interested I have alot of Mobile 1 5W-30 Truck and Suv for sale. Between me and my wife I drive 80,000 miles a year on personal vehicles. I realize I don't have a 5 year old spread sheet with oil analysis from Ruby Rock Labs (name change to protect the innocent) or whatever but my engine is a lot quieter, doesn't use any oil and no tick at start up now. Also it meets warranty requirements for all GM USA and has a rated service life beyond what the factory OLM will advise which is what I use for service intervals. One other thing too...totally OT but I had seen several reports where Castrol GTX either was removed from the GM6094M or failed the test or some bull whooey. Saw that start in late 2007. As of June 2009 GTX DOES MEET GM6094M according to list put out by GM...(so does Edge...I also saw Mobile 1 but not Truck and Suv or EP) Truck and Suv states it does on the bottle...don't see it on the GM list though.