How accurate/inaccurate is the MPG displayed on the dashboard?

Yeah, every tank I reset trip meter, note what the car's telling me, and enter it in my spreadsheet along with the accurately calculated. And enter the (real) data at fuelly. One hundred tanks (~50,000 km) tracked now, and error pretty much steady at 7.5%.

 

My gen 2 was about 2% higher than fuelly
My v is 4% high.

 

After 13000 miles on my 2014, it seems to be about 3 mpg too high, give or take a little each tank.If it shows 55mpg, the hand figured tank using same pump carefully filled up would be 52 mpg.This has happened many times.

 

My numbers are similar, albeit percent a bit higher. If I have a tank where the dash says 4.2 (liters/100km) it's invariably 4.5 when calculated.

That was ONE good thing with our previous Civic Hybrid: if the dash said 4.2, calculated would 4.2, or 4.1 (better) sometimes.

It would be dead simple for Toyota to fix. It's pathetic, like the guy/gal that keeps BS'ing about something, except everyone knows it, they're only kidding themselves.

 

I figure my MID is optimistic by 7% on average and varies tank to tank. How full is "full"? A significant amount of gas can still be pumped after the automatic shutoff. Pumping in "a little more" to round the transaction up to an even dollar can make a noticeable difference. An additional 0.2 gallon can knock off 1 mpg.

 

Yes, but in a tank or two, it will even out. Calculation errors die out quickly.

 

mine is dead, straight up, on.

 

I've found the average displayed on the dash in various cars high, low and spot on so I don't count on them. I track miles on Fuelly for reporting and paying attention to any serious dropoff indicating a mechanical problem but other than that I just drive and refill the tank at 1/3 or 1/4 of a tank left. No chance of running out of fuel that way and I alway have peace of mind as a result.

 

same here.

 

Mine consistently claims it burns 95.0% as much as it actually burns. That's a long-term, properly weighted average that doesn't move more than a couple of hundredths of a percent with each fill-up.