Shown MPG vs Calculated off by 1.5mpg

andreej · June 1, 2016

Filled up the tank and reset the trip on my new Silverado last week. Drove 441 miles. Gauge on that trip page shows 21.5 MPG. Put just over 22 gallons in though which comes out to 20 MPG... Is it really that hard for the computer to measure fuel flow and get this exactly right? yes, there is the variable about how full it was filled both times - I tried to be consistent but even if that was different by 1/2 gallon it wouldn't account the for difference.

anyone else check their's on a regular basis??

fondupot · June 1, 2016

Filled up the tank and reset the trip on my new Silverado last week. Drove 441 miles. Gauge on that trip page shows 21.5 MPG. Put just over 22 gallons in though which comes out to 20 MPG... Is it really that hard for the computer to measure fuel flow and get this exactly right? yes, there is the variable about how full it was filled both times - I tried to be consistent but even if that was different by 1/2 gallon it wouldn't account the for difference.

anyone else check their's on a regular basis??

Yes. Every car I have ever owned has been off. Some more than others. My 2011 F150 5.0 was off by up to 3mpgs sometimes.

My truck is pretty close though, usually within .5 to 1mpg off.

Nathan79 · June 1, 2016

One thing I found when I had a 2012 with the 5.3 is that the more it was in AFM the more it overestimated the mileage. It's almost like it couldn't properly calculate the mileage when it was in AFM V4 mode.

andreej · June 2, 2016

Interesting, thanks! My '08 was always right on, guess I just got lucky..

gmckenzie · June 7, 2016

I've kept track of what my DIC shows vs what I calculate and I've averaged the DIC being ~3.5% overestimating mileage. This is over about 6,000 kms.

elcamino · June 7, 2016

The psychology of fuel economy. Makes the owner think he is getting better mileage than he really is and thus he can justify buying the truck. People even get better than the EPA estimates on the window sticker, which is unrealistic and they really believe they are really getting that good a mileage all the time.

TJay74 · June 8, 2016

Hand calculated my truck is getting right at what the invoice sheet showed. That is way better than the 2010 truck it replaced that was even BB tuned and the best it ever saw was 18mpg on the highway.