How accurate are in-car MPG computers?

[yh125d]

Op you need a much bigger motor to get good mileage on the highway. This is where larger engines actually help. Your car was not meant or designed to get good mileage at that speed. It's impossible.

Which is why I got 5mpg better in my auto fusion :|

 

[LTC8K6]

Yes, drop a 6.1L hemi in there, that will improve your highway economy...

 

[yh125d]

Over 378 miles I used 14.925gal. That's 25.33mpg, when my trip computer said 26.5.



Woe is me

 

[Eli]

Over 378 miles I used 14.925gal. That's 25.33mpg, when my trip computer said 26.5.



Woe is me

I wouldn't really worry about a 1.2MPG difference, though I guess that is 5% off, which sounds more significant.

I consider the FCD in my Insight to be highly accurate, and I think it's +-1MPG.. so don't feel too bad, i'd say its pretty good.

 

[yh125d]

Woe regarding the MPG, not the accuracy

 

[Eli]

Woe regarding the MPG, not the accuracy

Ah. 😉 lol..

Yeah, I feel your pain. When I was a courier, I was driving ~7000 miles/month, and averaging 26MPG in my Focus. That was killer, at about 900$/mo in gas @ ~3$/gal.

That's why I was so interested in the Insight when the Focus was totalled. Quickly dropped my gas bill to ~400$/mo, which was a huge savings.

And that was when I first got the car. I've since learned how to get much better than the ~55-60MPG I was averaging back then. My record tank is 78.2MPG over 800 miles.

Have I mentioned that I love my car? 😉

 

[LTC8K6]

What sort of miles were those 378? City, highway, mixed at what percentages...

 

[yh125d]

About 85% highway (of those highway miles evenly split between ~81 cruising speed and 70 cruising speed)

 

[ViviTheMage]

My audi is pretty good, I like to watch the real time monitor. ..I can see where I am losing my mpg when accelerating.

 

[BoberFett]

The one in my Mark VIII is fairly accurate, and it's amusing to see it when I accelerate. I can quickly take it from the 28 I get on the highway to low teens when I get on the gas. 🙂

 

[LTC8K6]

About 85% highway (of those highway miles evenly split between ~81 cruising speed and 70 cruising speed)

See now I would call that good mileage for that car...

 

[PhoKingGuy]

My VWs is pretty darn accurate, i'd say +/- about 1 MPG, its usually a little on the conservative side of things. A pic from a few days ago:

I ended up getting like 540 out of the tank

 

[BurnItDwn]

I average more than that with my AWD 2010 Outback.

Anyway, the MPG computer in my car is usually ~1 mpg too high.

Outback has CVT, which makes for a nice boost ....

my 08 Forester probably weighs 500-1000 pounds less and has a similar engine (2.5 boxer), and usually gets around 25, but I don't have an OSD telling me. (I just divide miles by gallons every time I fill up and reset the trip odometer.)

my last car (Chrysler 300M) was accurate to within 1 mpg for the average.

 

[bunker]

Older thread but I figured I'd chime in.
In my '06 fusion, I got 31 mpg on the freeway @ 70mph.
At 80mph, that drops to 25.5 mpg.
Automatic, 4cyl.

In my new '10 fusion I can't seem to get better than 27mpg. Doesn't help that I got the manual transmission and it's just so much more fun to drive 🙂.

The computer in both shows anywhere from 1.5 to 2 mpg better than actual.