Hey guys!

Yesterday I purchased my first Mustang its a 2010 V6 Premium Convertible with only 5600 miles on it so like new!

I reset the trip calculator and drove about 60 miles so far and noticed the MPG is staying at 15 to 15.5 even on the highway!!

How accurate is this calculator?? I mean I didn't buy the mustang to save on gas but I was kind of expecting a average in the low 20's for highway driving. More or less I stayed around the 65 mph speed and tried to keep it steady didn't do any crazy driving.

Any thoughts on why it would be so low?

 

Best guess is it's still averaging for the entire 5600 miles rather than the 60 you drove. Plus, the computer is constantly learning. Meaning it adapts to the driving style. If the previous owner beat it to hell and drove it hard, the computer is going to assume that's still what is going to happen. I have heard from a guy who works at a dealership that a few people came back after buying a car wondering why it was so low, and that was one reason given. Give it some time to relearn your style, and drive it more to bring up the total average

 

Well the calculator is probably just off. When you fill up next time try hand calculating your average mpg. It's possible that there is something wrong with the car, but I kind of doubt that.

 

Thanks guys. This weekend I will have the chance to drive it some more and will try the manual calculation to see what it really is doing.

 

ya its possible the last owner drove in the city alot and floored it between lights
both of which would lower the mpg (or even just slowly crused around with lots of idleing)

 

Mine is always fairly low as well, although the majority of my driving is in the city...and when it isn't I drive "spiritedly," but I have heard that the readout is usually a little off.

 

The on-boards on the 05-10's are typically off by about 1-2 MPG on the high side but there are a few that are pretty close. My g/f's '06 is almost dead-to-nutz on at each fill-up whereas mine averages about 1.5 MPG off to the high side.

One other thing that may cause a low reading (other than some mechanical issue) would be if the previous owner changed gears or made a drastic tire size (O.D.) change without adjusting the PCM.

Averaging fuel mileage takes many, many data points; not just a 60 mile drive. Reset the on-board at each fill-up to get the most accurate info (as accurate as the on-board goes). You should be averaging mid to upper 20's if your pump-to-pump is all highway at or below 1800 RPMs.

 

Give it time to adapt to your driving style

My on-board is usually within .25 of my hand calculations. I reset it each time I fill up.

 

BTW, you can verify that the gear and tire settings in the PCM are correct by comparing your speedometer to a GPS. If your speedometer is off by no more than 2 MPH at about 60 MPH then the problem is not with gear or tire sizes throwing the on-board off.

 

the on-board on mine seems dead on
each time I've bothered to do the hand calc its matched up although I've been driving a few more slow roads lately so the on-board dropped