Any suggestions appreciated. I have a 2014 5.0, it’s at 90k miles, typically I would average around 17mpgs now I’m averaging 10-11mpgs. Haven’t changed driving style. Other than the basics, clean air filter, check tire pressure, so on so forth. Any other recommendations I should look into to improve gas mileage? I have a cold air intake, recently cleaned the mass air flow sensor, changed spark plugs, tire pressure good, air filters clean. Not sure why the sudden drop.

 

the MAF sensor does send a signal to the ECU to trim fuel leaner
.
...and I would not monitor fuel mileage by the instrument cluster readout it is unreliable as you probably know
17 mpg seems kind of high to me
I would expect maybe 14 ? but then I havent tested a 5.0
my old '98 Toyota Tacoma 4cyl really only got 16-18 mpg
2F150 5.4 12-14 which is why I went back to the f150

 

I have a very well worn 2010 XL with a 4.6 3 valve and 6R80. My suggestion as a starting point, is to check the fuel trims and MAF readings with a scanner (can get a cheap handheld on Amazon if you don't already have one). If you have a vacuum leak somewhere that's leaning the intake stream out, the ECU might be lengthening the injector pulse time, which will increase fuel consumption. You can check for a vacuum leak by spraying some starter ether or carb cleaner around the intake to see if the idle speed increases. Be careful though, no smoking and avoid hot exhaust components. I had a slowly changing (for the worse) fuel economy and traced it back to a crack in the small rubber fitting behind the intake manifold. Another possibility is the fuel "filter", which I believe is only the pickup strainer in the tank. A ten year old truck has had a lot of fuel going through it so that might not be as efficient as i used to be.

 

I sorta had the same problem. Youtube cleaning the throttle body.

I decided to do everything.
I cleaned throttle body, changed all spark plugs, cleaned maf sensor, and changed thermostat.

My highway mpg went from 12.8 to 16.5.
which one actually fixed it, iono.