Reduced MPG after oil change

TBleo · Jan 6, 2022

Hello Everyone,

New Guy here.
I wanted to post this to see if anyone else has experienced the same thing and/or what you all think the issue might be.

I recently had a routine oil change done and a couple of days after I noticed my MPG going below normal. I usually average 19 (70% highway 30% city) normal everyday driving conditions and 17 if I drive a bit more aggressively.

Now it’s having a hard time staying above 16. Average is 15 and it has even dropped to 12-13.
The truck feels like it’s braking when I let go of the gas instead of “coasting” like it used to do. It feels like I have to step on it more than usual when I want to accelerate.
At first I thought it was the tire pressure since temps dropped and my tire pressure went from 43-38 but I adjusted the pressure and still feels the same.

I have 22k miles on it. Pump regular unleaded. Same drive routine every day.
Any idea what this could be?

I want to take it into the dealer to have it checked out but feel like they won’t bother checking it if no check engine light is on.
I drive the truck every single day so obviously I know when something is off.

Thanks for any input.

T_Warren · Jan 6, 2022

Honestly same here man. I performed my own oil change and tire rotation this time around. Adjusted air pressure to 42. Noticed the same decrease in mpg. The weather has dropped in temps. I’m going to ride it out a week before I start worrying. Just thought it was ironic that someone had an issue around the same time

TBleo · Jan 6, 2022

Interesting. So I wonder if it’s simply bc of the cooler temps.
I did a bit of googling and the list is endless. Bad spark plugs, fuel injectors, fuel filter, intake valve, fuel pump, etc

T_Warren · Jan 6, 2022

That may lead you down a rabbit hole. I also noticed a pretty stout crosswind on the highway. But there could possible be something going on. Likely the temps tho.

Nthe8$ · Jan 7, 2022

Something else to consider is we're running winter blends of fuel. The blend evaporates easier due to the colder temps to help in starting and to run smoother. This blend has less energy which produces lower MPG's.

Jmzvet · Jan 7, 2022

I agree

tommysf13 · Jan 7, 2022

this past month I replaced my air filters with K&N. the week after my mpg dropped. I googled also and cold weather seems to be a common culprit. it has gotten even colder the last couple of weeks and mpg has dropped more despite more highway miles. I will have to ride out the cold and then assess

TRDBo · Jan 8, 2022

TBleo said:
Interesting. So I wonder if it’s simply bc of the cooler temps.
I did a bit of googling and the list is endless. Bad spark plugs, fuel injectors, fuel filter, intake valve, fuel pump, etc

I have taken my boss on several trips from Minnesota to NW Arkansas and Oklahoma. It is interesting to watch as the temps warm up, the MPGs can be effected by as much as 3 MPG just from ambient temperatures. The power will significantly improve with the colder and more dense air, but you will see a drop in my experience.

Edktm · Jan 12, 2022

It’s the garbage fuel and winter temps.. don’t get to nervous…

T_Warren · Jan 14, 2022

Agreed with the temps. This past week was above 40. MPG’s we’re back to normal.

TBCal21 · Jan 18, 2022

Same with my fuel economy. I went from 17-19 MPG down to 12-15 MPG since the last oil change. I live in SoCal so it would surprise me if the cooler weather is indeed the culprit.

TRDBo · Jan 19, 2022

TBCal21 said:
Same with my fuel economy. I went from 17-19 MPG down to 12-15 MPG since the last oil change. I live in SoCal so it would surprise me if the cooler weather is indeed the culprit.

What is the difference in ambient temperatures between the two oil changes?