i would not put 5W30 in the MDS hemi. You're better of extending oil change for a few hundred miles, until you get a chance to go get the 5W20, then you are changing to 5-30 now. Granted its a small chance, but if that oil clogs the mds oil passages because its thicker and wrecks your motor, it wont' even be warrantied since the wrong oil is directly responsible.

as for the 10w40, i wouldn't be in too big a hurry to go do it right now, but i would dump it. with winter coming, you dont want that 10 stuff in there when starting, the startup wear will btie you after a while. plus, the 40 is hurting your gas mileage too.

 

Pappy_FB had a deal a year or so ago where he could have gotten a case of 5w-30 RP for a "steal" and called the dealer and asked about it in his '06 Hemi and the dealer told him if he EVER had an engine issue and ANY viscosity other than 5w-20 was found, he could kiss a warranty repair good-bye.
So, especially you guys with the newer trucks and the lifetime powertrain warranty, I'd think twice about anything other than 5w-20!

 

I wonder if that's what my truck had in it before. I don't notice my mileage getting any worse since I put it in. But it's still doing horrible on fuel.
I think I'll run the 10w40 through until sometime in November, then dump it and put in 5w20. Just going to have to buy my own stuff. And I need to ask my grandpa what he has in his Dodge. Because he gets like 15 mpg in his truck with nothing done to it. I have exhaust and CAI, and I get 10.7.

 

i broke down and took the 5w30 back and got the 5w20. i noticed that a dealership said that if someone brought a truck in with a burned up engine that had anything but the recommended 5w20 that it would not be covered. i went throught ny manual and warrenty book and the only thing i could find regarding oil coverage was that the 5w20 was "recommended" and nothing was said that another viscosity oil would void the warranty. i would think that if it was that important that it would be stated that way. but it isnt.

 

well what that dealer is telling you is crap. the oil being the wrong viscosity has to be the cause of the failure, otherwise they got nothing. though if you got an engine that is all sludged up, or got scuffs or crap like that, it can very quickly and easily point to viscosity.

however, since the MDS uses small oil passages and such to activate/deactivate, i'd be more inclined to follow their recommendation to avoid the viscosity being a cause of failure to begin with, not just because it voids warranty.

 

Never understood why people want to use what's not recommended by engineers who designed the engine tolerances for a certain thickness of oil.
Back in 89, my brother in-law spun a rod bearing in his 28K mile Chevy pickup because he ran 20W50 in an engine built to run 5w30.