Okay so I bought this truck in December it had 104,000 miles in it and was getting roughly 16-16.5 mpg. I have 111,000 on it now and I’m averaging 13.5-14 mpg. I changed the oil bout 200 miles ago,cleaned the maf(which was absolutely covered in dirt,replaced the air filter with a k&n(the air filter that was in it was absolutely disgusting,probably couldn’t pass water through it it was so clogged up). What is goin on why am I getting worse mpg now with a new air filter and clean maf than before when the were absolutely filthy? I’m assuming the plugs have never been changed....
Any suggestion are greatly appreciated

 

Plugs an plug wires ? Coil packs ? Changed at any recent time ? And is Pcv working ?

 

There are no plug wires just coil packs. I have no idea if and when the plugs have ever been changed. I bought the truck with 104k miles on it. The only thing I found in the glove box was oil change records. I doubt the pcv valve has ever been changed. I will be be replacing the plugs and pcv valve very soon.

 

When I had a similar issue even after changing plugs, I found the throttle body and plate were gummed up. I used Seafoam on a rag to clean it out right on the truck. World of difference.