Just bought a new 2013 EX-L 4-cylinder three days ago, and noticed the next day that the earliest trip on the history display was one of 15.0 miles with only 7.3 mpg.

If I loaned my car to someone else and it came back with a 7.3-mpg trip on the display, I'd want to know what on earth they'd been doing! So I'm wondering the same thing in this case, even though it took place before I ever laid eyes on the car. (The odometer reading is 71, and the visible trip history adds up to 69.0 miles, so apparently the car had been driven just a couple miles before the trip in question.)

So, is this normal? Worth following up on? Evidence that I should get a life?

Thanks,
Jim

 

Running the engine during factory checkout? Moving from factory to storage lot, to another storage lot, to railcars, to trucks, etc? That kind of stuff gets poor MPG.

 

lots of idling?

Having no shortage of family that works at dealerships, you can't rule out some lot lizard didn't romp on it moving it here and there, washing it etc, but I imagine they do a bit of idling thru the shipping process, pre delivery inspections, etc.

I wouldn't worry about it too much less you notice something wrong.

 

And I'm still a fan of the tried and tured method of filling the car up, setting the trip or writing down the milage......drive a good bit, at least to less than 1/4 tank, fill the car up and divide the miles driven by the gallons to re-fill to calc the MPG.

Compare the manual method to the car computer for several "re-fills".....if the two are close then have some trust in the computer.....I'd still do a few self checks every now and then.

 

On a recent trip of > 700 miles, my trip computer overestimated my mileage by about 10%. That's pretty far off, isn't it?

 

Yes and no. The thing is, unless you're measuring the fuel in whole tank intervals, your error rate will rise significantly (in other words, if you went 500 miles on the first tank, and then refilled after driving the next 200+ miles, your error rate will be potentially fairly high). Why? Because different pumps click off at different points so you can never be sure exactly how much fuel is in your tank.

FWIW, I tracked my mileage a few years back on a vehicle which had a computer, and after maybe five or six tanks a trend emerged, the OBC was about 2% optimistic regarding my fuel economy. That said, after about 100 tanks of fuel I saw some very interesting swings, from -5% up to 9% errors for individual tanks, however, the overall error of 2% never varied. What this proves is that the tank was less full than normal after some fuel stops, and more full after others.

 

This was based on 2 fill-ups. I will continue to monitor the mileage. If I were to get only 2% error, I would be pretty satisfied. Time will tell. I'm curious as what other factors may affect this, like the type of tires installed on the vehicle. I am driving on what came with the car and their pressures are at the recommended level.

 

Tires, oil, and other mods will not affect the calculation error; only the fill-ups.

When you say 2 fill-ups, were you filling empty(ish) tanks or tanks which were say only half to three-quarters empty? That makes a big difference as the smaller amount of fuel relative to the one to one and a half gallon difference from where pumps click off will definitely skew the calculation.

 

The tanks were at about the 1/4 mark. I put in a total of about 22.5 gallons.
How could tires not affect the the odometer? Smaller radius => more miles registered on the odometer, right?

 

Sorry, I thought you were referring to different brand of tires, not different sizes. Yes, if you change the diameter of the tires, you will introduce speedometer, odometer, and MPG calculations errors.

As for the refueling, 22.5 gallons means only a little over 11 gallons per fill-up, and given that the click-off point of different pumps can vary by as much as a gallon and a half, that is a significant percentage of the total.

Were I in your shoes, I would track and compare the miles divided by fuel versus the OBC for at least ten tanks of fuel to determine the standard error; two tanks and 22.5 gallons simply isn't a large enough sample size.

Edit:
I see that the tank size of your car is listed as 17.2 gallons; to minimize calculation error during your ten tank test, it would be best of you would drive the car all of the way to near empty before refilling.