Gm has there own sythetic brand now I think its called Dextrose? Anyways I think thats the stuff blue cajun 5.3 is thinking about, I personally just use mobile 1 motoroil, and ac delco brand in the diffs

 

Dexos approved 5W30 is recommended oil for your truck. It's in your owners manual. I got tired of the cold start rattling and piston slapping at about 10k miles and switched to RP 15w40. No more rattle no more cold start slapping.

 

I like Pennzoil Platinum synthetic.

 

The piston slap when it first starts up drives me crazy. Might have to try this next time I change my oil

 

Your stock 6.2 has piston slap...?

 

Just used the syn blend at the dealer. Last time I use the dealer for anything. Bunch of trained (sort of) monkeys there. Idiots. It's a shame that when the economy went **** up, all the good dealer techs went to the private end to make there money. Warranty is no good to me if I can do a 1000 times better job myself.

 

No more slap and rattle on my 6.2 since the change to 15w40. But it is already close to 100 degrees here. Would not be so sure so far up north. What are your highs and lows this time of year? Mine will make lots of noise on cold start up under 50 degrees on 5w30. Not so sure below 50 degrees on 15w40. Will have to wait and see.

 

I've ran amsoil 15/40 extended change diesel oil in mine since day one no rattle and I have heard a few 5.3's 6.2 that are kinda noisy when it gets cold outside.

Bottom line almost anything you put in it is good stuff as long as it's name brand run what you want and you will be good to go. You are bound to already have a preference of oil you like using by now so go with it.