This weekend I took my first road trip in my Fit (albeit a shortish one). I was curious to see what my MPG would be on the trip up and trip back so I filled up before I left home and then filled up before my return trip.

I drove 110 miles on the first fill and 103 on the second. The route was mainly 2-lane back roads and 4 lane highway in Virginia with speeds between 55-65. I didn't use A/C and occasionally cracked the windows.

My when I filled up before heading home, I got 30.8 MPG by my calculations (miles driven divided by gallons pumped). This seemed off since my average over 5500+ miles is 34.4. I then drove back, filled up and calculated 57.2 MPG. The route up and back was the same, as were driving conditions, driving style, load, etc. The only difference is the gas pumps used.

Has anyone else experienced this great a fluctuation? My only conclusion was that the first pump, second pump (or both) are inaccurate.

 

pumps vary a lot at what fill level they shut off. The first pump may have shut off at a high level and the second shut off at a low level giving a wide difference in gas pumped. Accurate results require averaging over many fills.

I don't think the actual amount of fuel shown vs. what was pumped would be inaccurate, but it's possible.

What did the Fit say? (avg mpg)

 

That makes sense about the pump cut-off being different. The first fill was 3.6 gallons and the second was 1.8.

Unfortunately I didn't look at the Fit's meter before resetting the trip after the first fill. I did look at it after the second fill and it read 39.8 - probably the most believable of any of the numbers, as much as I'd like the 57.2 to be correct!

I should note, though, that I filled up at same station before my trip and when I got back.

 

Hand calculations will vary, since it won't always fill exactly to 10.6 gallons. I find the MPG display to be accurate, so I go by that.

 

Steve's right that gas pumps will vary somewhat in when they shut off. For a full tank, this doesn't make so big a difference, but when it's only a quarter of a tank or so, it can be significant.

The average for your entire trip (213 miles and 5.4 gallons) is about 39 or 40 mpg, which sounds entirely believable and in line with my experience.

 

The same route in different directions isn't the same route.

Even if the start and end points are the same elevation, the slopes of the hills you did hit will probably not have been identical: climbing the steep side of a hill and cruising down the long, gentle far side will give better mileage than climbing the long uphill and braking down the short, steep side.

Next time you go there, you'll probably see similar results.

 

Add wind as a big factor unless it was calm both ways

 

I did a trip from mid-Phoenix out to Wild Horse Raceway Park (used to be Firebird Raceway). I expected about 36 MPG, and ended up getting 30. What the hey? I filled up at out local Quick Trip (where I always go) before I went, but went to Chevron when I got home. Really do think it was the gas pump. My dash readout said 36 MPG, but my calculations by hand said 30. Argh

By the way, the Fit booklet has a great web site, www.toptiergas.com, that lists stations with detergent gasolines (recommended by Honda). Turns out Quick Trip, Costco & Chevron (I go to all 3) all have detergent gas. So, even the gas itself could be a factor in MPG.

BTW, doesn't the gas tank have a sensor in it that tells the nozzle to shut off? I just fill it until nozzle shuts off and take my readings from there. If this is the case, wouldn't you get the same amount of fuel each time? Or is it a sensor in the nozzle????

 

It's all in the nozzle, and the shutoff can vary somewhat with different pump designs and nozzle adjustments and so forth. Just imagine what would happen if it were something in the tank that could break down and not get repaired, especially with all the people who don't pay too close of attention when they're filling their cars. (Yes, the mechanism in the nozzle can break down, but the gas stations are a lot more likely to keep it working properly than every random driver is to make sure their car is in tip-top shape.)

 

In truth the automatic cutoff of gas nozzles varires a good bit depending on the nozzle and your filler pipe and the angle between the two.. Its the back pressure from your filler pipe and the sensitity is pretty wide for filler nozzles. After refilling did you notice if the fuel gage indicator was 'full' the second time.
In fact the only way to insure you accurately measure mpg is to weigh the whole car before and after filling and divide the change in weight by the specific gravity of gasoline, which youmay have to do yourself. Cumbersome. Otherwise average mpg over a number of fillups and you'll get afair idea of mpg's but comparing back to back is not very useful.

 

well said.

 

My fit avgs about 37-40mpg but drastically change for the worst with heavy winds or hills. On my daily commute to work I can easily get 38 consistent. But says a vegas run with all the cross winds and headwinds plus hills I'd be lucky to pull off 33-35. Both instances are based on 75mph cruising speed. I've gotten as bad as 18mpg rampaging through GMR canyons in manual paddle shift mode.

 

I'm not sure of the accuracy of pumps and or stated fuel capacities because there has been a couple times I've filled 11.2 gallons and the car was still running fine when I pulled in and I'm not the one to "top off" gas, I wait for the click and then go once more then it clicks again and that's done.

 

The accuracy of the amount of gas pumped is very high; the problem is refilling the gas tank to precisely the same level. Its hard to do even when you fill to the top of thefiller neck due to trapped air.
When you run a good economy run you weigh the car after fueling and again after refueling to the original weight. And of course watch out for those who add weight during the run that isn't gasoline so refill to weight is less than proper. Surely no one would do that. Surely.