I have a 2005 GP and the owners manual says to use 5W-30 even at temps well above 100F. They specifically state not to use 20W-50. Who are they kidding? Since when is 30W oil acceptable for temps over 100F? They either are smokin something funny or purposely want the engine to spin as free as possible for fuel economy standards. Never have I ever used 30W for anything close to 90F+. I'm more interested in protecting my engine rather then getting 1 MPG better mileage.
Does anyone have comments or are running with anything heavier?
Thanks,
Tom

 

It's better to contact the dealer and confirm first before moving on.