So, I just did my first "serious" fill-up, and put in 13.3 gallons for 348 miles travelled. (Not bad at all, 26.2 mpg ). However, the MID said I got 28.4 mpg on that tank.

I wasn't expecting razor accuracy, but that's almost 10% off (8% actually).

Over on the VW groups, the consensus is that the trip computer calculations for average mpg are always too high. Have TSXers found this to be true also, or should I wait and see for a few more fill-ups -- obviously differences in how much gas was put in can make a big difference.

(Note that I tried to search before posting, but you can't search for "avg mpg", at least not in a way I could find )

 

I think I read in the manual there is a way to adjust it......could be mistaking with something else though....

 

Yes, others have mentioned this as well. I don't have MID or navi to calculate mpg though, so I just always calculate it myself.

 

I only have like 1500 miles on my car which is only a few tanks of gas, but my MID has been within 1.1 MPG +/- every time so far. I am getting BAD gas mileage, but its been consitent regardless thus far. Although right now it says 17.2 MPG

 

Stop hitting redline every shift.

 

Well, 1.1 mpg on 17.2 mpg is still an error of 6.4%, whereas the figures I quoted above are an error of 7.8%, in the same ballpark in terms of accuracy.

Has your MID ever told you your MPG was worse than what you calculated using (miles driven)/(gallons to fill tank)?

I bet it does better when the mileage is accrued at highway speeds. In the city when coasting, the "inst mpg" goes "off the scale" (e.g. 60 mpg plus) over short distances travelled. The error in the calculations when this happens and you're not going very fast (e.g. coming to a stop) is certainly higher than when steadily cruising at highway speeds.

 

I haven't even hit the VTEC switchover yet (but am getting closer)...

 

not just a wee-bit, but quite a bit!

In metric measures, my MID sometimes ends up showing as low as 6.8 Litres/100KM at the end of a tank which is unbelievably great(35mpg), but with manual calcuation it ends up being 28mpg which kind'a pisses me off.

I've got real 30+mpg tanks out of my TSX but the MID was still way off on those ones.


Another electronic f*** up by a car manufacturer I guess.

 

I dont understand why its so difficult to get a digital reading of how much gas is left in the tank. I guess thats the problem with the MID though. It seems to be doing a "best guess" as to how much gas is left in the tank, divide that by the miles and there's your mpg.

 

Yes, it is always somewhere between 1-2 mpg 'optimistic' for me.

 

oh yeah...this also reminds me that being that our odometer reads 5% too optimistic as well...our mpg is even worst.

 

I do 95% highway driving: MID mileage ~34-35MPG, actual mileage 30-33MPG. It is _always_ high.

 

maybe it's just to make us feel good or get close to the "epa fuel rating"

 

My results are almost identical.

 

I seriously only hit vtec about 1-2 during the week if that.....That 17.2 is the lowest MPG its ever read so far and its cause i haven't hit any other roads except my commute, so no highways to help kick it back up.


rb1 - It was worse one time by .9 MPG otherwise it has been better reading than what i actually calculated.

 

My impression (but I don't really know), is that it was calculated by gas consumption measured via a flow meter versus miles driven.

You can reset the MPG in the middle of a tank of gas. However, this still isn't definitive, as a computer could still calculate MPG by just storing an estimate of the remaining gas at the time of the reset as the new "baseline". But then again you can also add gas to the car and not reset the MPG meter also. (It could still detect that you had added gas and reset it's baseline automatically, so again this isn't proof of the way it works).

 

I guess it doesn't help accuracy when Honda/Acura odometers are themeselves 2.5% off.

 

Supposedly they have tightened this up some recently (not sure if this was the 2006 or 2007 model) -- maybe this has something to do with that settlement they just made.

I did notice when I passed one of those automated radar/speed signs in a neighborhood recently that the speedometer itself seemed very accurate, within 1 mph, but I'll get the GPS out in a few weeks and double-check it. In my last car, the speedometer was off exactly 3 mph high (not speed dependent), but the odometer error was less than 0.5%.

 

My MID shows about 2 mpg more than I am getting based on fill-up calculations.

I used to have a 1996 Miata and the speedometer showed 10% fast at any speed. I was always calculating in my head. 60 was actually 54.