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Does the Trip Computer Lie About MPG?

idavidsonidavidson Posts: 41
edited April 2014 in Mitsubishi
Just took possession of new 2008 LS with V6.
Only 40 miles on the clock when I took it.
Reset the trip computer and began the 160 mile
drive home all highway.

At the end the trip computer stated:

Average speed: 57 mph (this is true since I babied
it the whole way down).

Average mpg: 34.2

This last figure sounds bogus since the v6 is rated
by the EPA 20-30 mpg and no one has reported
such a high figure before. Could it be wrong?
It was just me in the car cruising at 55 mph for
a bit then 63 mph for a bit and so forth. Never
reved the engine about 2700.


  • comem47comem47 Posts: 399
    I've never seen above 30MPG on my LS V6 4X4 (high 20's yes, but what you got sounds highly untypical (my meter displays a running average) I don't know if it's possible to get into an "instantaneous" mode in which case you would also see like 10 MPG when you floor it. The display always resets when unused for over 4 hrs in which case you start all over again with 0.0 MPG and 0 MPH, etc and quickly rises in the first few miles for MPG, but average MPH takes a while to catch up even on the highway (you cloul be on the highway doing 70 and it still is saying like 45 MPH average )
  • I parked it overnight and it reset as you describe (as an aside you can
    turn off that feature).

    This morning I drove 1 mile to get on the freeway (said it
    used about 15 mpg) then 25 miles on the highway at 55 mph
    (the average mpg crept upto 33mpg) and then one mile on suburban
    streets to get to work (average mpg crept down to 32.5mpg).

    Could it be because I'm babying the engine? It's in the burnin period
    so I'm accelerating very very slowly. Just staying in the right hand
    lane, not overtaking, steady at 55, 58mph. Getting lots of fingers and
    rude signs, but that's another story!
  • comem47comem47 Posts: 399
    "I parked it overnight and it reset as you describe (as an aside you can
    turn off that feature). "

    I have a 2007 and I found that while the manual described a way to change it, the mode resets when you turn off the ignition, so I was always back to square one. Many people (at least with 2007s) are frustrated that you can't keep a running total average MPG over a tank if say that tank takes you 5 days . (to be able to get up in the morning and still find it at the last reading of say 25 cumulative MPG, vs going though it displaying like 15 mpg till you have driven maybe 20 miles to bring the new average back up) If I drive it enough miles on the highway before shutting it off the reading is pretty close to what you actually are getting by taking the trip odo miles divided by the fill up gallons, but otherwise the indicated MPG will be much lower than actual (not enough time so display a real average)

    Note that I do not have the Nav package, which I believe gives you better access to programming features.
  • toomanyfumestoomanyfumes S.E. Wisconsin Posts: 1,004
    I've tried babying it on the highway to get the highest mileage possible and have never gotten above 29 MPG. (2007 LS V6 4WD)
    2012 Mustang Premium, 2013 Lincoln MKX Elite, 2007 Mitsubishi Outlander.
  • > I've tried babying it on the highway to get the highest mileage possible and have
    > never gotten above 29 MPG. (2007 LS V6 4WD)

    Okay, so its not out of the realms of possibility since mince is a 2WD.
    Also, it was just me (200 pounds) and nothing else.
  • Hi,

    Just finished my first tank of gas.

    404 miles, 12.5 Gallons put me at around 32 mpg.
    But as I said for the first 300 miles I babied the engine.

    As an aside I did two experimental trips:

    25 highway miles at 55 mph: I got 35 mpg according to TC.
    25 highway miles at 50 mph (the manual recommends this as
    a speed to maximize fuel economy): I got 40 mpg.

    But let me tell you that driving at 50 mph on CA highways is
  • I don't put a whole lot of faith in the computer .This may sound stupid but I have notice driving to and from a destination that the MPG coming and going at the same speed and conditions can vary by 3-5 MPG. I usually never go over 60 mph . I guess the best way to judge is to fill the tank complety and replace the used gas and then divide by the miles driven . By the way , the best I ever got was 29 MPG and I have the XLS 4Wd .
  • Let's just say that the computer is 'optimistic' - usually by 2 mpg at least.

    I don't think it's fair to quote anything but the mileage that you've calculated based on miles traveled / gallons used. Anything else is phony.
  • The only true measure is miles driven / gallons consumed.
    But it seems that the trip computer is fairly accurate approximation
    to that based on what I've seen.
This discussion has been closed.