buckeye4

Interestingly my 2017 DIC calculates my mpg at almost exactly at a 5% higher rate than actual. I have a excel program that calculates my real gas mileage based upon actual miles driven per fill-up. Not rocket science as I just record miles driven and reset my tripmeter to zero (for next fill-up) and record the gallons issued at the pump. Speedometer and odometer reading are very accurate. The problem is the DIC under estimates the gals used at 5% giving the 5% error in average mpg. Gallons used always shows less than actual. Database is 55 fill-ups. OEM tires and wheels. My 2014 gave very accurate readings. Anyone else have this issue and can it be adjusted?

taz2016

My 2017 Z51 DIC averages about 1.5 MPG higher than it actually is. I never use any car's computer calculated mileage as I've only had one (Acura TL) that was accurate. The inaccuracy is not random but appears to be by design. Every other car I've owned has read higher than the true mileage. Some by as much as 3 MPG.

Tom/99

My 2015 DIC also averages about 1.5 mpg higher than actually calculated.

Patman

I'm surprised it's not perfectly accurate because I have heard more than one person here state that their "fuel used" feature is perfect. So if that calculation from the DIC is perfect then the MPG calculation also should be perfect. With any car you need to average out the MPG calculation over many tanks in order to factor out the fact that you might not fill your tank to precisely the same level every time

LbulletM

I use the "fuelly" app (well, it's actually a website, I just have the link saved as an icon on my home page) to calculate real world. HIGHLY recommend in lieu of a spreadsheet.

Catman74

My 2008 C6 DIC always read 1-1.5 mpg better than the actual calculation. My 2017 GS seems to following the same pattern. My wife's 2015 Toyota Highlander readout vs. calculation is pretty much right on the money...for what that's worth.

dvilin

Place me in the minority as I never bother to check.

Billy346

My Prius tells me the real-time gas mileage. It's a huge gauge right in the middle of the display where the Corvette has a tach.

My Corvette tells me how many revs the engine is turning. It's the big gauge right in the middle where my Prius has a fuel economy gauge.

When I'm in my Prius, I think about fuel economy, when I'm in my Corvette, I try not to grossly exceed the speed limit.

tail_lights

^

Mine is higher on the DIC as well. Not sure how many tanks but it is 27k miles worth

FunDriver

I haven't checked, and would like it to be accurate of course, but whatever it is will be ok with me. It's already known to be great for a car with this much horsepower. So as long as someone doesn't run out of gas relying on it, it's probably not a major problem.

mountainears

+1 for Fuelly, although I use the actual app.

To me it is not that big of a deal. Use an app or the DIC. If the DIC is off, but consistently off, then it is still a viable tool to indicate that something may have changed and alerted you to that change.

But if you're looking for accuracy, I've always been one to track off the odometer and what I know the pun says has gone into the car which is something the cars computer simply can't know. This is why I choose to use an app.

Vetteman Jack

There will be some kind of fluctuation since it is hard to put back in the same amount of fuel as you started with. But I agree that the DIC average seems to be a tad high compared to a hand calculation. It happens on my C5.

fnbrowning

It's worse than that. In the years I've owned my Corvettes, I've tried,
- Going back to the same station/pump/nozzle multiple times
- Different stations & nozzles
- Auto shutoff from low fuel fill rate. Auto from high fill rate.

1 to 1.5 gallon error in favor of DIC average, means an algorithm is designed to give an illusion of higher mileage than IRL.

While the built in error is not Earth-shattering, it is likely along the line of the other tweaks exposed lately that have been done by auto manufacturers to bolster emissions numbers.

Is their numbers fiddling lawsuit fodder? It might be fun to explore the possibility.

buckeye4

My initial concern was that my miles driven was being recorded at a 5% higher rate than actual and shorting the warranty by 5%. The actual problem was the fuel used calculation and not the odometer which is very accurate. Curious as my 2014 was dead on.