MPG dropped after oil change

So I had my oil changed last sat and now my mpg is horrible. Before I was getting 18-20. Truck is 15 with 35,000 miles. Any ideas

 

Who changed it (dealer, friend, chain store)? And did they use the correct oil weight?

This happened to my previous car (VW Jetta). Dealer changed oil and my MPG went to shit. I later changed it myself and the MPG went up significantly. I had no idea what the dealer did. I'm assuming the VW dealer didn't change my oil filter, just drained and refilled oil.

 

Probably just a fluke. I'd give it a couple more tanks before I started looking into it.

 

Did you get the muffler bearings lubricated? Additional friction in the bearings could be causing additional rolling resistance and increased engine load.

 

How do you track MPGs? Maybe the dealer, or whoever changed the oil, zeroed the mileage trip meter when they cancelled the oil change indicator which makes it look like you did less miles on that tank of gas. That's if you track the mileage per tank with your trip meter.

 

Dealer did it and I reset my trip myself. The muffler bearings are good. I have them changed when they do my blinker fluid

 

Did they do any other work? Maybe they unhooked the battery and reset the ECU..?

It could be any of many variables unrelated to the oil change.

 

Never had a problem mpg-wise with muffler bearings, would guess 15w-45 blinker fluid (heavier) or they lubed the tires (less traction).

 

No just oil change

 

This type of thing usually only happens with 3rd Gen owners.

 

Did they adjust your tire pressure lower possibly?

 

No pressure is good.

 

As someone else mentioned, one week worth of gas isn't anything an average, and it certainly isn't anything to worry about. I'd give it at least a few tanks to see what the average is and see if it has been affected.