My F150 3.5 Average MPG is dropping. New plugs.
I’m curious ?

 

3.5 EcoBoost? 3.5 N/A? Year, milage? You didn’t give us much info to go on.

 

 

WHY do these threads even exist???

 

Epic.

 

How heavy is your foot? My mileage goes down when my foot becomes heavier. I don't care though. Sport mode is fun as hell.

 

I'd tell you it's winter gas, but I see you're in Hawaii, so

 

I'm not OP but in a similar situation.
2016 3.5 eco boost, 4x4, 2 inch level, K02's 33's tires inflated to 40 psi
56,000 miles on vehicle
Spark plugs and air filter replaced in March 2026
15,6 MPG City prior to replacing plugs and air filter, no change afterwards.
(I've converted the miles and mpg to standard measurements)
Actual 90,000 km driven Gas mileage city 18L/100KM
Next attempt will be to clean or replace map sensors. If I can locate them.

 

@mark kr Here is the main one. There is also a MAP sensor by the throttle body and one on the intake just after the air filter. Pop those out and give them a good clean. Just be careful not to damage then thin sensor in the middle.

 

This is a 2.7 but the locations on a 3.5 EB is similar.

Red in the intake manifold, green before the throttle body.

The intake manifold MAP gets nasty, the MAP before the throttle gets oily, both can be cleaned with MAP/MAF spray cleaner, air dry do not touch them. To finish do a throttle/idle relearn.
Did you re-calibrate the speedometer and adjust the AFE in engineering mode? Both these should be done with the tire diameter change. KM