When I start the truck, before driving, I see the average MPG on the dash going down by 0.1 every few seconds. I haven't sat there long enough to see if it goes to zero yet, but I haven't seen the countdown stop either. It didn't happen before the last few days, no changes were made to the truck. It happens at stoplights also. 2019 Ecoboost Screw XLT.

 

its using fuel and not going moving

if the meter has been reset recently it going to make a notable difference until you get some miles on it so that time is less and less of an average

 

Is your auto start stop not functioning? When stopped with auto S/S enabled, the mpg won’t drop.

Obviously, if you’ve disabled it or it’s off for other reasons, you’re still burning fuel so the mpg average will be affected.

 

if you truck is running, but not moving, the average mpg will be (should be) going down.

The dash/computer readings are never totally accurate. The most accurate way to determine mpg is by hand/manual calculation (using actual gallons used and actual miles driven).

 

Three great answers - thanks!
Yes, auto start/stop is turned off. Can't stand it.
I'll take a longer drive to test it out. What all three of you are saying makes sense - I've been taking short drives lately, and sometimes resetting the mpg. I've been trying to get P04DB fixed and just had the sensor replaced which improved mileage. But the code still pops up after a full drive cycle. Nobody's been able to fix it and I'm on pins and needles just dreading that code coming back up, so I'm watching everything on the dash too closely it seems.

Thanks for saying it nicely, everyone. Duh .... lol

 

Which sensor was replaced?

 

Crankcase pressure sensor, which I think is on the same tube coming from the PCV valve. I'd have to check with my mechanic to say it more accurately.

 

Yep. I believe that sensor is located midway between the connection points on the driver side PCV hose. The passenger side PCV hose is smaller and just connects to the PCV valve. Thanks.