I think I'm seeing about 2.5 mpg difference - with the car being high, except one time.

 

My last fill had the car saying 38 and I actually got 36.7.

 

I'm seeing a similar gap. About 3 mpg difference, with the car reading higher.

 

According to the car's system, I've been averaging 41 MPG City & 47-48 Highway and only have about 700 miles on the engine. I'm very happy with this car!

 

I can't even touch that. Not sure that my driving habits are, but I think I get mid to maybe upper 30s. Better than my last car, but I don't have spirited driving habits either. I commute 10 rural miles with 2 stops in that stretch, with an additional 2-3 miles of in town driving.

 

I have 10,000 miles on my Fit now, and have not reset the Trip B miles since I took delivery - it indicates an average of 38.1. My "actual" calculations work out to 37.4, so it's not far off.

I run 87 octane from whatever station I'm near when I need gas, and mostly drive a 35 mile rural commute for work here in the relatively flat Middle West. I've made three long-distance trips (all over 10 hours one-way), and my mileage tends to drop to around 35 on those (70mph interstate). I don't hypermile, and don't hoon, either – pretty much drive the limit and enjoy the scenery.

es

 

I do leave ECON mode, mostly have the sunroof open and drive at speed limit (😏 sometimes haha) and don't even pay attention until I look over at "Info" and notice the high MPG.

On the subject of ECON mode, this is by far way better than my 2013 Honda Accord Sport on ECON Mode, when I drive that car, it feels really slow. This car it's real quick and honestly prefer ECON on. 😄

 

Hondas generally get better mileage after 5-10 k miles, an unofficial break-in. That's been my experience with 3 previous Hondas.


BTW, are any of you guys spiritually related to Mr. Monk? Talk about OCD. Mileage depends on a whole host of variables, including time of day, temperature, if you use the same pump, atmospheric pressure, and whether the pump cuts off the same each time. Do you top-off the same each time? What is the current blend (summer/winter)?


I generally fill up when the little yellow icon pops on the gauge, about 2 gallons left. I've never pumped 10 gallon into the Fit, a range of about 35 miles left. Got stuck in a 45 minute traffic jam yesterday and the mileage dropped to about 29. There are no old fashioned traffic cops around who know how to direct traffic.

 

Car said I got 42.2 but manual caculation said 38.2.

Im not sure if the pump is correrct or the car.

 

(Bold added.) This is the huge variable that many posts in this thread ignore. ("I just put X gallons in after Y miles so my MPG was Y/X. The gauge said Z so it lied.") The amount of gas you just put in this fill may be off from what you just used by a gallon or more based solely on this effect. Also whether the car was level or not at the pump and, if not level, what its attitude was. And whether you clicked the pump/topped off after shutoff. (My wife doesn't. I do.) And on and on. In my experience, this effect is more or less the same on all cars. So the calculated MPG impact is larger on cars, like the Fit, with smaller fuel tanks. A half gallon +/- on a 9.5 gallon fill at 375 miles swings the MPG from 37.5 to 41.7. The same half gallon +/- on a 17 gallon fill only swings MPG from 21.4 to 22.7.

For this reason, the dash display--which knows about the amount of gas actually injected--is probably a much better information source until you have at least three, and six would be better, tanks worth of pumped quantity data to average out all the variables of how full you actually got the tank on each fill. My '07 CR-V has used 2,132.84 gallons to go 49,667 miles. I'm betting that the errors from individual fill quantity are pretty well nulled out when I calculate the purchase-to-date MPG at 23.29.

OCD? What OCD?

 

I'd bet the pump was correct about volume of gas dispensed.

But, for reasons just described, using one fill quantity replaced to tell you about MPG experienced--and gallons actually used--has lots of error sources.

 

Probably both. Use the same pump next time and stop pumping the same way you did this time.

Dick W- Accurate numbers ain't OCD. The only disorder is spending more energy worrying about something than you're willing to put into studying and measuring it. If you're going to care, care enough to matter or just admit that you don't care and shut up about it.

 

OCD is Obsessive Compulsive Disorder. If you ever saw the "Monk" series you'd understand better. Mr. Monk was a former police detective turned private consultant because of an emotional trauma. Tiny things, details, distracted him. Stripes left by a vacuum cleaner running counter to his preferred pattern drove him wild, would steam clean each set of bristles on his tooth brush separately. Actor Tony Shalub.

 

Check.

Where on this scale does having the data for 18,785 gallons/1,428 fill-ups of gas consumption for 10 vehicles owned since 3/17/92 fall?

When we moved here, we had to ship our car in the container with less than 1/8 tank of gas. So as the day got nearer for it to go in the box, and I was trying to aim for the low tank on the right day without knowing how far we were going to drive before that happened, I stopped completely filling it. (It went in the container showing something like 11 miles of range.) To keep from polluting all my data, I ended up accumulating all those partial fills until I filled it when we got it back on the other side. Then I had to wedge my spreadsheet to ignore this one data point showing over 1,000 miles on a total of two and a half tankfuls of gas when calculating my Max Fill Qty value for this car. Still makes me a little crazy. This is probably higher on the OCD scale.:wink:

 

I'd have split the numbers into three tanks on the report because I'd rather have my outliers show underperformance.

 

At the time I didn't keep track of the per fill miles on all the partial tanks and didn't reset Trip A until the first to-the-top fill-up here; but, now that you say it, it occurs to me that I could use the MPG for the whole span of partial tanks to back into miles per fill values for each of the partial and then the to-the-top fills. This would eliminate the MaxFillQty wedge and the get the correct accounting of the number of gas stops. Decisions, decisions…

 

Some Important points:

1. Automotive odometers aren't all that accurate. They are usually a couple of percent low.

2. It is virtually impossible to fill the tank to the same level repeatably. Again, it will vary by a couple of percent.

3. The on-board MPG indicator is only an estimate, since there is no fuel totalizer in the system. The fuel used is calculated by the EFI's injector's on-time which only approximates the fuel used. Also, the MPG indicator uses the odometer for distance, see item 1.

You can generally trust the accuracy of fuel pumps which are regulated by government weights and measures agencies. If you calibrate your odometer against a known distance or with a good GPS then you can calculate your MPG over several tankfuls to get an accurate value.

If you're simply dividing the pump reading by the trip odometer reading your numbers are likely off by several percent. Worse, one fill-up won't be comparable with the next one. You'll convince yourself retroactively that one thing or another caused an increase or drop in MPG when in reality the change was within the inaccuracy of the information.

 

To which I would only add that the odometer cal also varies continuously as the tires wear. The same wheel revolutions--what the odometer actually is measuring--will carry you farther on new tires than bald ones.

 

Good point. New tires have a radius of about 12 inches and a tread depth of 0.7 inches. Wear them out and the tread depth decreases to 0.1 inches so your radius is 11.4 inches, a difference of 5%

I generally keep track of my mileage using the odometer function of a Garmin GPS that is hardwired to the vehicle power. When the car is running the GPS is recording distance and it is quite accurate. I tested it by comparing the GPS readings to measured distance standards. That way, tires, wheels, and odometer inaccuracy are negated.

 

I fill up X amount of gas at the pumps
I pay Y amount of dollars for the gas
The car travels Z distance before it needs to be refilled.


I don't care what X is as long as Y is low and Z is high.


Those are the numbers I use :P