Fast Deceleration

Hey guys. I have been having some serious bad gas mileage. Highway is about 15mpg. I do have 265/70/17 LT general tires. I do have a 2525xl (I think that the model) muffler. I am coming up on 60k miles. It is a v6

When I get off the throttle it slows down fairly quickly. It seems to be getting worse. When I step on the gas it seems to be sluggish unless I mash on it. But still quick to slow down. Almost like the pedal is heavy. Any ideas

I did order gear fluid to do xfer case front and rear diff fluid change. But otherwise will have dealer do rest of stuff like tranny flush.

 

Did you just change your engine oil? My milage goes down a lot, to like 13 mpg for a couple weeks after I change engine oil. Then it slowly goes back up after the oil gets circulated for a couple weeks.

 

Does it roll easily on a slight incline in neutral? If not you your brakes may be seizeing possibly your parking brake is stuck on as well

 

Will try that in morning. Don't have a jack otherwise would lift it up and see

 

Well i tried it and checked parking brake it rolls fine.