Last week I bought my 1st Fit, a new LX 6 speed and am very happy with it. But after I drove it for 3 days I looked at the mpg for Trip A (which was reset when I picked it up), it had 101 miles @ 38.2 mpg. The dealer put 34 miles on it before I bought it, so the total (Trip B wasn’t reset) was 135.6 @ 29.7 mpg, so 25.2% of the total miles (34) that the dealer put on, averaged 4.4 mpg if my math is correct? The dealer claims the low mpg is not accurate because of idling time and moving cars around due to snow storms. Does idle time would factor into mpg if it wasn’t moving? It seems to me idle time will only show up in lower mpg in an actual mileage check.
Can anyone offer a reasonable explanation? Maybe my math is just out of wack. I keep thinking that someone beat the snot out of my new drivetrain. I appreciate any of your thoughts.

 

Why would you think the computer would not include idle time in its mpg calculation? It's just dividing the distance traveled (from the trip odometer) by the fuel used (which it knows since it controls the fuel injectors) since the last reset. Anytime the car is sitting idling it's using fuel but not traveling, so its gas mileage at that point is exactly zero mpg Sufficient idling can make the average gas mileage as low as you'd like.

Your math isn't correct, as well. 101 miles at 38.2 mpg equates to 2.64 gallons of gas used. 135.6 miles at 29.7 mpg is 4.57 gallons. Subtracting shows that the dealer went 35.4 miles using 1.93 gallons, or about 17.9 mpg average for that first bit. That really doesn't sound at all out of line to me for idling and maneuvering around a parking lot. I don't think you have anything to be concerned about.

 

When I got my Fit it had only a couple of miles on it. They said they started the car every day and occasionally moved it around the parking lot. So yeah, they burned a lot of fuel before I picked up the car.

The mileage you get is what matters, not what they did.

 

The drop you are seeing is normal. I have posted many times here the dates of RVP change that happens after Sept 15th in most areas of the country. That is your biggest drop. If you want more info. go look on the EPA web site. As previously posted in this thread there are also many other factors the negatively affect your mileage in colder weather.

It will come back up next April.