Unless I'm calculating MPG incorrectly (miles driven / gallons of gas added to the tank), my MPG computer thingy is calculating my MPG incorrectly.

For the record, in case I'm asked for cliarification --
When I fill my tank, I clear out the trip meter. Then, when I fill it again, the number of miles that I've driven between fill-ups is the 'miles driven' figure that I use in my calculation.
The number of gallons that I'm putting in to my tank on this fill-up is the 'gallons of gas' figure that I use.

*I can re-explain if that's not clear.

Is anyone else having this issue?

My MPG computer reads that I'm averaging about 39mpg. After calculating it out manually (using a calculator), I'm finding that I'm actually averaging about 35mpg.
Neither figures are anything to complain about, of course.

 

If you read the other MPG thread that's been quite recent, a lot of have people have noted that the on-board computer overestimates the fuel economy. Your method of calculation is the same as mine, and of course it's a somewhat rough estimate but is decent. I think the Canadian one has been a bit more accurate, not sure if it's because it uses L/100km rather than MPG, but on my first fill, a quick calculation yielded an economy of 7.1L/100km whereas the computer quoted 7.0.

Also I believe the meter is only good for your most recent driving habits, not so much from the whole tank or your driving to date. The reason why I say this is because I was driving on the highway, for about 5-10 minutes and managed to drop my fuel economy reading from 7.0 to 6.7-6.8 (L/100km of course)...which suggests to me that it averages your economy based on your most recent driving activity. Does anyone else have any other possible explanations?

 

Computer seems to be about 10% high on average.

 

Mine is 4mpg almost every time. But next time use the Search function.

 

I just use the display as an indicator of approximate mpg. I don't think these are accurate on any car.

One other problem in determining accurate mpg is the small tank. Your fill up is likely to vary by a small amount which can cause your manual calculation to be off as well.


Love the car!

Dave

 

Actual Mpg = Computer Mpg - 4

That's my formula and it's pretty consistent regardless.

 

I know its not going to be completely accurate but always being over by 4mpg is pretty bad engineering/programing on hondas part. The avg mpg on my mustang was better, it was accurate to +/- 1mpg.

 

So I guess Asians aren't all that great at mathematics.



I'm Asian.

 

Yeah, but wouldnt' you like to have 4mpg more?

 

My recent road trip showed 40.3mpg on the computer. But actual Asian calculations proved only 35mph. But I'll still tell friends and family I'm pushing 40mpg. Just because.

 

mine isnt as inaccurate as other people's but still inaccurate nonetheless, my trip computer said 37.5 but actual was 35.3, still not bad IMO

 

The number of number of miles traveled indicated by the odometer is reasonably accurate and at least it's quite consistent. However, the number of gallons pumped may vary depending on which gas station you choose and of course which pump you use at that gas station. Pumps can go out out of calibration and this may be a source of discrepancy that you didn't consider.

Calculating your fuel consumption despite the variables is probably more accurate than the reading off the MPG computer.

 

Mine seems to be almost exactly 10% above the actual value each time.

 

Folks! tell me how you get this 40-ish mpg thingy. On my first tank the computer says 32 and the real mileage is 28. ok at least that 4 mpg extra thing is correct (yes the formula works) but how the hell did i get such low low mileage? I don't drive w/ a lead foot (iron foot maybe). I drive mostly in town. many stop and go high traffic situation and a lot of very short drivings - like 1-3 mile trips around town for grocery, etc. does that kill the mileage? Actually the worse mileage happened AFTER I filled up the tire w/ air. Go figure.

I still love my car but this mileage thing is disappointing. the last honda I got from the same dealer (a civic) also had low mileage. maybe that's it - the damn dealer is the evil spirit that haunts my car's mileage! Should I bring it back to check it out? The problem is it's still w/in EPA range.

 

Your mileage sounds low, even if you're driving it like you stole it. (Did you?)

Do you have AT or MT? If you have a MT do you keep the revs high all the time?

How many times have you filled up your car? If it's just once it could be the different pumps.

 

The first couple of weeks, I drove pretty much only to work and back (highway). I also was breaking in the car. I averaged (on the computer) between 38 and 40. After break in my wife was driving every other day (in town only) and it dropped to 35-36. I filled up on Monday and she drove it Tuesday about 25 miles in town and the computer read 27 this morning. The best I have gotten so far (calculated) was 41.8 on a trip, pure highway, no stops. I wonder how many people are driving in town only and what milages they are getting.

I am totally happy getting anywhere above 32mpg (real mpg). It is still about 5mpg better than I normally got in my GD3.

 

During my weekday commutes, in LA driving, my computer averages around 36-37 mpg, or roughly 32-33 calculated. The weekends bring up that average for me by about 2 mpg.

I've gotten 46 mpg on the computer on a high-wind 70 mph highway trip from Vegas to LA.

 

That's the root cause of your lower mileage right there.

 

1-3 mile city driving should yield higher mileage than what he's getting. That's why I stated my LA city commute mileage which is much higher than his.

 

No I drove really slow, and try not to hit the pedal/break hard. I have an automatic. I don't know how to drive a stick shift. The last car I had was a Camry and it had great mileage (around 40mpg on the highway), better than my previous Civic.

I have only filled up my car once. But from what others have posted their first tank was much higher. Granted my first tank was filled by the dealer and I don't know what kind of gas they used.

An interesting observation: my dealer had filled my tires to only 25 psi. At a little past half way mark the low tire pressure light came up so I filled them up to 34 psi. At that time the average mileage on the computer was 33 plus (30 in real life according to the formula). Then the rest of the tank somehow on those properly filled tires I achieved much lower mileage. At the end the average mileage is 32 on computer and 28 calculated. I did end up diving mostly very short distance trips after half way mark so I wonder if typical trips to the grocery about a mile or 2 away is a mileage killer.