Bad MPG on s197 mustang

Hello everyone,

My 2011 mustang v6 is getting pretty awful gas mileage. According to the display on the dashboard it’s getting 11 mpg around city with light stop and go. Haven’t taken it on the highway in a week so no exact numbers at the moment for that.

The display is also reading the message “check fuel fill inlet.” I’ve watched a few videos and tried cleaning it with seafoam as recommended and then reset the message but it keeps coming back.

There is no obvious damage on the fuel fill inlet (the 2011s use a capless fuel system.) Other than the car getting bad gas mileage there is no check engine light or any other symptoms. I’ve checked for a fuel leak but found nothing. I’m not smelling gas either while i’m driving or walking around the car.

I’m just not sure where to start

A bad/broken thermostat that’s stuck open can cause lousy fuel mileage.



Questions 1. How long have you had this Mustang 2. Have you checked the mpg the pen and paper way to know what it really is. 3. Have the dash read outs been reset after a fill up. 4. Why not take it on a highway trip and see how close it does to the EPA rating 5. Any chance that you are driving like you are late all the time.

Wild guess would be a bad purge valve. That would account for the “fuel inlet” message anyway.

Or a 10 year car has a faulty fuel filler flapper seal. It happens.

I agree with the thermostat thought.

Also it might be dragging brake calipers that are stcking or a master cylinder that has gone bad and making the front or rears brakes drag.