Was in local Wally-World the other day. Mobil 0w40 was no longer on shelf. Looks like 5w40 is what I'll be using on future oil changes.

 

Well, I think I'll be chiming in here for the What-Its-Worth department. I have the LPW, so if it says in the engine compartment to use Mobil1 0W40, then by gawd thats what I will use. Chrysler may or may not want to cover any engine problem down the road and they could use any excuse to deny a claim. Regardless, I also add two 15oz bottles of STP at every oil change. If you ever get any of that on your fingers, you'll see how hard it would be for it not to stay on all moving surfaces in the motor. That protection is golden, as the majority of damage in an engine happens before the oil is fully circulated at startup (in normal operations of motor vehicles). When a timing belt/gear set went south on my old 89 Park Ave, with 132K miles on it, the mechanics were shocked at the condition of the lower end. At that time, I was using el-cheapo wal-mart non-detergent oils and the wal-mart generic engine treatment (most likely repackaged STP, as it felt exactly like it). So, 0W40 and two 15oz bottles STP and I'm golden for as long as Chrysler covers any engine repairs not due to oil. Oh, STP stipulated on its bottle and in an email from them to me, that STP is fully compatable with any and all synthetic oils and directly with Mobil1 0W40. Maybe down the line (if Mobil1 0W40 isn't available anymore) I would have to switch but until then I'm sticking with the sticker!

 

Reading the manuals I see that 0W-40 and 5W-40 are recommended but adding anything to the oil is not.
So seemingly a warranty claim could be refused on that reason alone.

 

Not recommended yes, forbidden, NO...