Oddly High MPG

[Joes2silly]

I haven't been that good at checking my mpg or keeping track of my mileage when I fill up but lately I've been noticing something strange. A few weeks ago (maybe more) I filled up my tank and when I calculated my mpg I got 50! I don't remember the exact numbers but I think there was about 400 or more miles driven on about 8 gallons of gas. But today when I filled up I punched in the numbers and got 58 mpg (426.2 miles trip, 29.6 avg mpg, 7.3 gallons of gas). While I don't doubt the fiesta is capable of this, I am just wondering how I am getting such high numbers on mostly city driving and high-speed freeway driving.

[Aglie]

Unless you have been doing a lot of driving under ideal conditions, like steady state 50 mph, those numbers are too good to be true. I suppose it is possible there are 2012 tweaks that help, but more likely you haven't quite filled up the tank or it was overfull prior to the first high-mileage tank; or, perhaps your distance is off. Did you change your tires? Normally odometers are pretty accurate. What does your built-in gauge say?

[Norm201]

I had this happen to be several months ago. I filled up and normally I reset the counters before starting the car. I had forgotten after I started moving out of the gas station on to the highway. The system was in process of recalibrating my MPG when I decided to interrupt it and reset it as I was moving. Then I also started getting 50, 60, 65 MPG readings. I wanted to let it go just to see if it would calm down. But then I decided to reset it several times over as I was driving. That seemed to put everything back in order and my MPG came inline with normal readings of the past between 35 and 40 on highway.

[Joes2silly]

My tires are factory and the computer seems to be reading what my avg mpg should be (29-30). I know if you don't hold down the button long enough it wont do a full reset but I've made sure each time to fully reset the trip odometer, avg mpg, and avg speed. I also know for a fact that I'm filling it up all the way because I sometimes see a little excess gas drip out the vent (or whatever you call the hose running down from the filler cap). The only thing (if any) that I have done to my fiesta was pulling the F1 fuse earlier this month and driving without it for about a day but even that shouldn't have any effect on the odometer.

[FXSTi]

Has anyone else driven your car? Maybe they added gas.

Try keeping a record of mileage on a site like Fuelly | Share and Compare Your MPG That should help you to know if those numbers are right. If you have a smart phone get the app Fuellog so you can record your numbers at the pump. Fuelly lets you submit via their mobile webpage or sms but I like to keep the record on my phone.

[iamz]

I would guess someone is playing a trick on you and adding gas to your tank.

[Norm201]

Originally Posted by iamz

I would guess someone is playing a trick on you and adding gas to your tank.

What? With the price of gas? Pretty expensive just to play a prank!

[Pennut]

Big tail wind maybe?

[iamz]

Originally Posted by Norm201

What? With the price of gas? Pretty expensive just to play a prank!

A couple of gallons on a couple of tanks isn't all that expensive. Especially if they then siphon a few gallons on the next two tanks so he gets like 10 or 11 miles per gallon. Someone on Car Talk did this for real just to drive their neighbor crazy. Pretty funny.

[Joes2silly]

Conspiracy theories aside I'm going to keep a much closer eye on it and just see what happens next time I fill up.