I have an 03 ram 4.7 4x4 used to get 13 to 18 mpg now I get 13 or less I have an obvious power loss when the outside temp is above 80 degrees. I've done all maintenence, tune-ups, no codes everything appears normal except mpg and power any ideas what the problem is? any help would be apppreciated........

 

Partially plugged cat converter perhaps?

 

Dirty EGR valve?
Dirty throttle body?
What oil are you running?

 

I've ran castrol full synthetic since I bought the truck new. As I wrote before its worse when its hot outside seems to run better when the temp outside gets below the low 70's anything above 80 it gets worse