Average Fuel Economy Calculation

[09CRVEXL]

My CR-V trip computer seems to only look at the last 100 to 200 miles of data for average fuel economy. I am still gathering info on this, but I was trying to keep my Trip A as a lifetime average fuel economy, and I reset Trip B when I filled up. So far, the two values converge after 100 to 200 miles.

A and B reset upon delivery of new CR-V (8 miles).

Filled up after 150 miles, and both meters were at 23.7 average.
Reset trip B at 150 miles.
At 300 miles total:
Trip A: 24.9MPG average, 300 miles trip
Trip B: 24.9MPG average, 150 miles trip

Considering that the first 150 miles of Trip A was at 23.7 average, there is no way mathematically that both could be at 24.9 after another 150 miles.

Has anyone else noticed this?

[rapieper]

I am thinking you have too small a sample - or something.

My A is used for per fillup and B is cumulative of the last 4000. A is showing 5 miles since fill with an avg of 26.7 ; B is showing 25.6 .

Keep checking - if your experience does not change you might check the dealer.

[Black Pearl]

I use my B to track each tank and A for special trips. So A frequently has hundreds and at times over a 1000 miles if I haven't done a special trip for a while. I have never really checked them against each other per se, but they seldom read the same average MPG.

Welcome to the club. Hopefully you will get your mpg indicators straightened out.


EDIT: I thought I posted this here last night, but it was in another thread. Loosing my mind.

[09CRVEXL]

Thanks for the responses. I've switched to letting trip B roll for longer distance and reset trip A per tank.

I can't wait for snow to fly, and I'll start towing my snowmobile trailer. That should get me well below 20mpg average. :eek:

[rlb2444]

I owned a Prius before buying the CRV. I learned to drive the Prius to maximize the mileage. I have maintained the same driving procedures and I think the mileage is exceptional in the CRV considering the size. Although I have only relied on the on board computer to track the mileage it seldom drops below 26 and most of the time it's in the mid 27's. 90% of my driving is in town. On the highway it is not uncommon to see it at 33 to 34 depending on the terrain.

[chocho]

I'm not sure if it's the hilly roads or the oddly placed stop lights in my town, but my mpg displayed on the dash for my new 08 CRV AWD LX seems to be too low. My Trip B is for miles driven since my last 250-mile-long, 90% Hwy trip, and Trip B has been 70/30 City/Hwy and its mpg is consistently getting lower and now it reads 16.8mpg (combined with Trip A, average=21.5). Is this normal?

I thought this was too low, so I calculated mpg myself (second to last full-tank fillup odometer - 550mi, just last fillup odometer reading - 694mi and I filled the tank with 9.5 gallons. (694-550)/(15.5-9.5) = 24 mpg). 24 mpg seems to make more sense than 16.8mpg that the dashboard displays. Did I do the calculation wrong or is my car really guzzling a lot of gas?? I'm not sure if the dashboard mpg is all that accurate. By the way, I'm not an aggressive or impatient driver; I follow all the tips on how to get the most mpg out of my car, i.e. starting up slowly and going 55-65 mph on highways.

Thanks for your help in advance,

[Black Pearl]

Welcome to the club!. The calculation that you showed was 694-550 divided by 15.5 - 9.5. = 24. Alas, good math but in the wrong direction.

Make sure I understand you. You filled up at 550 miles. Then you filled up again at 694 miles. That is a difference of 144 miles. When you filled up the second time, you put 9.5 gallons in the tank. Is this correct?

If so your mileage is 144 miles / 9.5 gallons = 15.16 mpg. Not too good.


When you calculated it, you divided by the amount of gas remaining in the tank. To see your error, assume you drove 200 miles or 300 miles--what ever you like. Assume that you put 14.5 gallons in the tank. By your method, you would be getting 200 or 300 miles to the gallon. You should have divided by the amount that you put into the tank, which was 9.5. So your problem should look like this (694-550)/9.5 =15.16. Not very good mileage, but at least your dash display is in the ball park. They usually read a half to 1 mpg on the optimistic side from what most members have reported.

Does the above make sense? You drove 144 miles and you consumed 9.5 gallons. So your MILES PER GALLON is the distance you drove divided by the amount consumed driving it, which is the amount that it took to fill the tank up.

So the next question is why are you getting so lousy mileage? Are you warming up you car a lot, or sitting in traffic jams? That is not great mileage. You might try switching brands of gasoline.

Welcome to the club, and I hope you can improve your mileage!

[chocho]

Blackpearl, thanks for the prompt reply. You ARE correct that my calculation was incorrect;) Wow, that IS a really bad mileage.... I have no idea what I'm doing wrong... Is it the heater? I tend to put it on high for several minutes until the car warms up then reduce it. Well, I guess I do stop a lot at the lights when I drive around. Or is it the cold weather? Perhaps it's just me. But I don't really know what I'm doing wrong...:-( I mean, my CR-V is good in the snow and it snows a lot where I live, so I'm glad I have it, but the mileage is not that great for me...

[Black Pearl]

The fuel mixture changes in the winter and you don't get as good mileage. If you warm up your car, which you are not supposed to do according to many, leave the temperature control on full cold--it will warm up faster. I don't think it matter when the car is warmed up what you do with the temperature control, unless your sitting in traffic.

If you use the same brand of gasoline all the time, try a different brand. You can check your mileage. Take a trip on an interstate, say 50 miles, where you can go the speed limit. If you don't speed, and your not caught in traffic your V shouldn't have any problems getting mid to high 20's.

Traffic jams, cold weather, winter gas, starting and stopping, and warming up the car all take tolls on the fuel economy.