I have a 2003 SRT 10. 10W-30 Mobil 1 is recommended. The newer Vipers use 0W-40. I plan to use 5W-40 synthetic in my 03. Is there any reason that I shouldn't?
There was a discussion years ago suggesting to use the recommended oil manufacturer
and weight because the oil manufacturer's blend is specific to the auto manufacturer's specs. (suppliers, producers, etc. bid on those auto contracts).
In other words, the difference between 10w30 and 5w30 may or may not be only the weight. At least that was the chemist's in that thread said.
From a business perspective it also makes sense. If meeting the auto manufacture's specs to produce 10w30 is more costly than their run-of-the-mill 5w30, then an oil manufacture is apt to not put the same additives, etc. expense in the 5w30.
Don't slam the messenger. I'm not in the oil biz, nor am I a chemist. I'm just relaying what I've read by someone who is a chemist.