Are there other variables in determining mpg for each tank. I would think the computer would know how much fuel runs through the lines and it knows how many miles traveled, so why is my mpg so far off. I've had two tanks where the mileage was at or just above the calculated reading, but most are 7-10% on the low side. This doesn't seem very accurate for a computer in this day and age.

If I were to fill up from reading the calculated miles for the tank I would definitely run out long before I get to zero. It is calculating my tank miles according to the overly optimistic mileage. I would just like an accurate reading. All tanks are filled at the medium fill speed and shut off at the automatic stop.

Can Acura reprogram the computer?

 

Miles/Gallons/MID Ave/Actual Ave

406 14.27 30.7 28.45
471 15.41 31.7 30.56
497 15.64 34.2 31.78
411 14.33 31.6 28.68
455 14.12 32.0 32.22
466 15.28 33.6 30.49
503 16.36 33.6 30.75
439 13.28 32.3 33.06
508 15.97 34.7 31.81

 

I have similar results to you... generally 1 - 2 mpg better on computer than in reality. I average 27 mpg (reality) vs the 28.x on the display. 85%+ city driving.

 

hmph mine seems to be accurate, don't know what to tell you lol.. do you ever watch your real time mpg? i'm pretty sure thats how it averages it so if it is a bit off its probably because that system doesn't respond immediately but its delayed by a second or half a second according to your pedal pressure, i dunno neve rbusted out a calculator though always do it in my head lookin at the receipt so if its close enough for me i take what the screen says. all I know is when my gas light comes on I have 2 gallons of gas left.. but it rarely if ever comes on cause i fill up at half

 

Are you guy driving until the gas runs out in the car?

If not how do you know exactly how much gas was in the car? How do you know when you first got gas that the pump did not kick off because it was close to full but not full? How do you know that the pump was calibrated perfectly for the amount of gas you got? How do you know that you got 0% water in your fill up?

Last all these things give you AVERAGE gas mileage not exact gas mileage! Every car forum I have been a part of in the last ten years have the same claims, so every car is wrong? It's Average, the computer can't average for the whole tank then be exact at the end of the tank. This is the same reason it can't show the last 15 to 20 miles in range when the tank is ending, it's working with averages and not perfect numbers.

 

There must be some formula or algorithm that is used to compute fuel mileage. I would just like to see the one on the dash lowered. I get excited when I think I am getting 34 plus mpg, but then really bummed when it is consistently 31. Why do I always have to subtract 3 mpg in my head to get an accurate mileage reading? I get on the highway and it states up to 37-38 mpg. I doubt this is even close. It's a joke.

As for whether I am burning fuel or water, won't this show up in reduced miles driven per fuel used? Doesn't the car measure how much fluid runs through the lines?

I think by documenting all the tanks it is very easy to see that almost all mileage is overstated. If I am down 3 mpg on one tank then down 3 mpg on the next tank wouldn't I expect to be about 5 over on the next not just .75 mpg? Only once have I driven to when the red light came on showing 60 miles left.

All tanks were Citgo 91 octane except the last which was Shell 91 octane. There is no higher octane in this part of the country.

I understand it is averaging the tank, but doesn't it recompute the total miles driven by the fuel consumed? Why does it keep taking a bad reading then then averaging a new reading with the bad?

When I see 34 I know its 31, when I see 31 I know its 28. Why can't this formula be adjusted or does Honda want people to think they are getting better mileage than they really are.

 

The car doesn't measure the fluid that ran through the lines, just miles travelled divided by an average fillup.

Like Cyberbro said above, in order to get an accurate reading you'd have to measure precisely how much you add and compensate for an overage or shortage. There can be a 1-2 gallon difference from fillup to fillup. The car can't account for how much fuel you add each time.

Calculate your miles driven divided by 14, then do it at 16.

It would make sense that any manufacturer would "ride the line" as aggressively as is legal in order to inflate their economy ratings. It's just business.