First off, this is not a "how can I get better mpg" post. My question is about the computer, and how accurate is it. No matter where/how I drive the display always reads 17.2/17.3/17.4mpg. Whether I'm on the highway, or in the city. It changes if i do a reset, but only then. Even with the reset it stays in the same range. How accurate is the computer? Am I doing something wrong?

 

Lucky, mine always stays within 14.5-14.9 no matter where I drive! lol

 

mine is pretty much always at 13.8

 

Not very accurate.

 

nice chart shotgun. i do the same thing for my truck. not sure what kind of phone you have, but i have a droid and now I use an app called "mileage" to enter my fillups instead of writing them down on a notepad like i used to. the advantage is i can export a csv file from the app, so i don't have to type my numbers into excel by hand.

 

When I got my truck, I set up a chart to track that exactly like Shotgun's. (Thanks shotgun by the way.) So far during my three fill-ups up to this point the differences between the truck computer and hand calculated is -0.88, -0.65, and +2.77. Was pretty surprised about how much off the last one was but it was in my favor so I'm not complaining lol

 

When I hand calculate mine it is usually within .5 mpg. When it is off the computer is usually the higher one. I'm not too worried about it though since the 99 F150 that I came from didn't even tell me my mileage. Plus this 09 gets better mileage too, so I'm happy.

 

I have kept charts similar to what Shotgun posted above for my last three vehicles. A 2003 Dodge Dakota, 2007 F-150 and now my 2010 F-150. The Dodge ironically enough was always within about .4 one way or the other. My Ford's are a slightly different story. My F-150s almost always show between .5 and 1.0 higher on the computer than manual calculations.

I am a bit **** about tracking MPG. I use the same pump as often as possible and always top off until even with extreme patience I can't get any more in. Yes I know topping off is bad but I always fill up before I drive somewhere which burns off a good bit right off the bat so I don't have to worry about expansion from sitting overnight or anything.

Sooo.. While some people on here and elsewhere claim crazy numbers it's rarely what I would call accurate. People that truly track it without bias are showing 15-16 in the city and mid 17s to mid 18s on the highway. My numbers track that way as does the data shown by shotgun. Just my $.02. Also relatively stable is the variance. There usually is one and it's usually in Ford's favor.

THAT SAID... It is relatively consistent in it's variable so if all you are tracking is whether you're doing better/worse and want a ballpark the computer is a great too.