Over the last month I have had my gas mileage drop about 2 mpg. Same driving habits, I buy only top tier fuel and have gotten it at the same two stations that I always use. Spark plugs changed 2-3 months ago, oil changed a couple of weeks ago along with oil and air filters. Tires are less than a year old, Air Pressure if good. Load has not changed.
No lights, no coes, no smells. My first thought was maybe a brake dragging, but I would think you would smell that but I haven't looked.
Just shy of 110K miles. All maintenance kept up. I've tried removing and reapplying my tune, I've completely returned to stock tune, nothing in that area seems to help.
I know it's kind of a needle in a haystack, but any thoughts on where to start looking?

 

Do you have a laser thermometer? Easier to check brakes with that than 'feel' or smell.

If you have forscan or another capable tool, check various PIDs to see what's happening. Maybe the fuel trims are off, some sensor could be screwing it up.

 

Clean the MAP sensors. The EcoBoost has 3 MAP sensors ....
And check the throttle body for carbon buildup and clean if appropriate.
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I failed to mention it but I just cleaned my throttle body and MAP sensors a couple of months ago, but I'll check them again.
Thanks for the reply!

 

I do not have a laser thermometer. I do have Forscan so I'll look there as well.
I'm planning and pulling the wheels and looking at the brakes. I should also mention that I replaced the Hub/Wheel Bearings and IWEs about 6 months ago. Maybe one of them was gone blinky. Another thing to check when I pull the wheels.

 

Is is possible you have a seized caliper making a brake drag ?

 

Do you know if they use blended fuel in your area? We have a summer and winter mixture that use different amounts of ethanol and a few other smog reducing additives and mileage changes with the seasons.
At one point last year my scan tool showed 18% ethanol in regular unleaded which is only supposed to be up to 10%. Grocery store gas so who really knows?

 

Well, the Ford ethanol percent calculation is not very good, either. It could just be wrong.

 

I really think that is something to do with it. My most recent fill up seems to have solved the problem. I'm thinking I had a bad tank of gas. Come to find out, the Shell station that I bought my last tank of fuel at suddenly closed down and they are pulling the tanks. It's back up where it normally is.
THanks for all of the replies.

 

In my experimentation the amount of alcohol in our fuel is a big factor in mileage.