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MPG Computation

887 views 13 replies 11 participants last post by  jfrullo 
#1 ·
These are my fuel usage stats from each full up
The fill up was at the same gas station
And the computer MPG was reset each time

The MPG column is the MPG computed by simply dividing the miles by the gallons used.
The Comp column is the reading the cars computer gave.

Gal Miles MPG Comp Error
12.1 266.6 22.1 21.1 -1.0
12.5 268.1 21.5 20.6 -0.9
12.5 278.4 22.2 21.7 -0.5
13.5 312.9 23.1 22.4 -0.7
12.1 296.1 24.5 23.1 -1.4
12.0 271.4 22.7 21.6 -1.1
12.1 280.1 23.2 22.2 -1.0

It seems the cars computer consistently reports MPG about 1 MPG lower that I compute by the old fashioned method.

My car is a 2013 V6 auto, base, no mods.
Driving was around town, some stop and go, some short freeway, some suburbia.
 
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#2 ·
Well that seems to agree with what I've read others have concluded from their computing also. The display shows about 1mpg less than actual. It's good to hear another confirmation of this. Thanks.

That means I likely get about 24mpg mixed driving. Sure beats the 13-14 mixed I got in my Dakota RT.
 
#4 ·
Mine is usually in the same range as yours, the computer is around 1 to 1.5 MPG lower than actual.
 
G
#5 ·
Me too. However, since I replaced gears, I've had two occasions where the computer was within a couple tenths below actual MPGs. Most of the time it's still 1-1.5mpg too low. My last tank reported 24.8mpg, but I calculated 26.68mpg.
 
#6 ·
I think what happens is that it over reports fuel usage. I reset the MPG meter and the trip meter at each gas up and in the trip meter menu it shows fuel usage in gallons. It's always higher on the computer than what I put in the tank so I think that's where the error comes from.
 
#10 ·
My 2012 v6 base manual, 5000 miles, also consistently reports 1-1.5mpg below actual at least on highway trips, usually don't track local driving.

Just got a 2013 Explorer so far computer was actually 1 mpg under then accurate next time for the 2x I filled up. It says not to track mpg until over 1000 miles.

My 2010 Toyota RAV4 was always spot on with the mpg comp. vs. calculated....
 
#13 ·
FWIW, since most/all of the replies have come from V6 owners, my GT's computer also typically under-reports by about one MPG, sometimes a little more.

IME the more consistent one's driving is, the more accurate the on-board computer is. That is, when a given tankful is all-city miles, or all-highway miles, the dash readout tends to be much closer to the actual calculation than if I drove, say, 75 miles in town, then did a 120 mile road trip, then did another 60 miles in the city.
 
#14 ·
19.2 is my best
muat of got a bad one
or when i drive i pound on it to much
it now has about 4600 miles on it.
2011 pp purchased new delivered 1/9/11
 
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