mrpositraction

Your partially correct. Still going to take the same amount of power to move the truck. Denser air, less throttle, get it?

Loki 5.0

Perhaps, but at cruise you still have to pull a set RPM for a set speed. If the load is not demanding a lot of throttle you are going to be using more fuel as that cylinder is going to fill with denser air and the computer is going adjust the A/F ratio. .

EBinMT

Winter fuels are reformulated with oxygen bearing compounds like methyl tertiary butyl ether. MTBE is great for octane rating and helping cold starting, but llike ethanol it displaces actual fuel compounds causing a need to burn more.

TopGun

My mpg have slowly declined since O have bought the truck, After leveling and putting bigger tires on the first day i got it, it was getting around 17 but has slowly been dropping about 1 mpg a month, granted I started driving it a little harder as i put more miles on it, and recently i got a remote start, but i always reset it each month and currently i am getting 9.8 mpg, im guessing its possibly the cold in michigan making my tires have less psi, the winter blend fuels, and my driving habits changing... but still, that sucks lol. almost at 5000 miles now ill have my alignment checked along with oil change and thourough check for all TSBs.

Goatlicker

I have the same issue, leveling kit with airbags, bigger tires, 25000 kms on it and fuel mileage decreasing ... Currently getting between 11 to 12 mpg... Not impressed!!!

EBinMT

you two are you own worst enemies for fuel mileage. increased ride height + bigger wheels = worse fuel mileage.

I am not saying you can't have something else going on there but those mods combined with colder temps, winter fuel and/or winter 10% ethanol fuel and you have a recipe for horrible mileage.

Remote starts alone are giving you 0mpg. if you let it warm up for 5min then drive 10min at 16MPG you average 10.5MPG.

mrpositraction

You answered your own question. The computer keeps the A/F at a given point, whatever Ford told it to do. The amount of fuel is determined by the amount of air the MAF sees and the load the engine is under.

So in your scenario, set speed, set rpm. If the air is denser, the throttle reduces to allow less in.

One way to look at it is the power to turn the motor with all the load connected (drag, accessory equipment, driveline loss, etc) If you are making more power than you need, the engine accelerates. If you aren't making enough power, the engine decelerates. If the air is more dense or less dense the computer is still going to try and achieve the same A/F given the load on the motor and throttle position.

So just because it is colder doesn't mean you engine is always making more power (your theory of more air, more fuel, less mpgs) , that wouldn't make sense.

Now to help everyone better understand this, if you could keep all things constant except temperature......this means truck configuration, throttle position, etc...............and the only thing you changed was air charge temperature/density, then yes you would use more fuel, but you would also be going faster

BUSCH

Getting 15.5 here in South Dakota. City/Interstate driving.

BLU4TJW

Ethanol + winter gas blows. Just a fact of life. I say we shut down all MPG threads till April, cause we'll all just be a little bit happier then.

DieselDawg

Find a way to stop cold air coming into your airbox AND put a grill block/blanket across the grill. Both will help with winter mpgs. Also, a fuel injection cleaner like B&G might be called for to remove carbon deposits from the Direct Injection. I wish the B&G was cheaper, but it does work.