Well i live on the prairies in Canada where it gets to be 35 degrees in summer and -35 degrees in winter. I run 5W20 straight synthetic all year round..... recommended by the manufacturer for the hemi engines, not sure if its the same for the 4.7L engines or not.

 

I just run Mobil 1 5w/30 and change every 5K miles. For filters, I've been using Purolator filters.

 

i live in southeast texas so you know its hot down here and i run 5w30 all the time with no problem.