I'm cruising at 65 just filled up and my engine light came on. Was getting 21 on the highway now I'm hitting 18. Truck is 08 quad cab 4.7l dodge 1500 with Cai,exhaust,and 22 inch wheels " if it matters" also rpms are normal about 18-1900 cruise set. Could it be a dirty filter?

Nvm I guess engine light is still on but I set cruise to 70 and I'm at 20mlg and goin up.

PCM has locked in a diagnostic code and needs to be read. Could be anything from the gas cap not being tight to a random misfire. Won't know till you have the code read.

It finally cleared at my next fill up I mist not have tightened the gas cap. I'll still get it read when I het a chance. Thanks