[jkhawaii]

Interestingly the calculated MPG is actually lower than actual MPG for my 2014 Cruze Diesel. 30 calculated, 36 actual. That's opposite what I usually see from those computed MPG numbers. That's good though 36MPG average is a lot better than 30MPG

 

[MP81]

Sometimes ours is lower, sometimes higher, and sometimes almost near the money. It really depends on routes you took, traffic, etc.

 

[pandrad61]

with hard records i do 33.2 mph 90% city and computer says 31 or 30 most the time.

 

[chevrasaki]

The biggest factor in a single tank calculation like that is how much gas was in there before and how much gas did you put back in. Averages are nice because it takes all those small discrepancies and ignores them. When you track a bunch of tanks you get a much more accurate miles driven per gallons bought ratio.

Note: Usually if my calculated mpg is higher than the computer, the next tank will most certainly be the opposite. I usually only calculate higher if I didn't fill the tank as completely as I did on the last fill up. (It's impossible to fill the tank to the exact same spot, or more every time. Unless you have an ever expanding gas tank. Sometimes you have to put in less fuel than you did before) My cars computer on average reads 3-8% optimistic

 

[MP81]

I record the DIC estimate as well as the calculated estimate, so I really should put together a chart and see the correlation.

 

[chevrasaki]

I record the DIC estimate as well as the calculated estimate, so I really should put together a chart and see the correlation.

If you spend the time to do this, I will spend the time to do this. Then we can get compare them. There's probably an easy way to export the data from fuelly into excel, then you should just have to add the DIC numbers you've recorded. Then you can manipulate the data in all kinds of ways and get some neat charts. I've also recorded the gallons used and the average speed each time too.

 

[MP81]

I have all my fuel logs in Excel anyway - that's how I calculate my city/highway percentage.

 

[weimerrj]

Mine is consistently - and this is over 2 cars (2 different 2012 Eco 6M) - 10% optimistic.

 

[ranger024x4]

I reset my trip computer as soon as I bought my car and have logged ~2700 miles with it. My computer calculated mpg's is currently at 30.5. Now about 500 miles after buying the car I started using fuelly and have a 29.5 average. I did spend the first 150 or so on the hughway and probably saw 36ish so i feel like its very close.

Also fwiw, i have used the gallons used to see if that was even in the same ball park and it was pretty close both times.