This is a 2 part Poll. First I would like to know How you calculate your MPG. Second, if you record it by hand what is the difference between your manual calculation and the trip computers calculation.


14 Votes in for a difference between hand calc and display with an AVG difference of .4286 (Mikie's vote added in by hand)


Database Analysis Info

529 Vehicles Checked (Completed)
Hand = 34.22%
Display= 50.47%
Mixed = 15.31%
AVG MPG w/.4286 per vehicle avg subtracted from display entry method = 36.21 MPG for the TCH

The database is reporting 36.5mpg.

While 50.47% of the data reported was calculated via the vehicle itself it really didn't skew the numbers that much (.29% approximately)

 

I have copied and pasted the information from the TCH database into a spreadsheet and gone through 56 vehicles so far. Here is the data I have so far. Hand Calculation of MPG = 33.93%, Display Calculation = 51.79%, Mixed Calculation Method = 12.50%. The last person I stopped at has an average of 40.2 MPG. So far you can see that in the higher reported MPG the majority of people are using the Display to report their AVG MPG. I will update after I have done more as there are a total of 530 vehicles and I have to click on each one to figure out how they report.

I plan on taking the results of this poll an obtaining an average of the difference between the display and the hand calculated methods and subtracting that number from the MPG reported by the people who solely record the MPG by the display method. I will then use that to figure out the overall AVG MPG from the reported vehicles and see how different my number is from the database number.

 

Don't forget to pick two options. 1 for how you calculate you MPG. 2 If you choose the Hand method what the difference is from the display.

 

You got a lot of time on your hand!
I'll save you the trouble, if I may, the MPG computer is 1-2 MPG high.

 

I calculate it by hand - the MFD display typically shows the tank average about 1mpg higher than I calculate. Once in a great while it will be about 2mpgh higher.

 

I'm doing this while I am multitasking at work.

On all 3 of my fill ups it has been -3. You're probably right that in the end it will be in that range. For right now I am going to plug in 1.5 into my formula. I am 99 vehicles so far. H=30.3%, D=58.59%, M=11.11%.

 

First of all, Dan, THANKS to the hard work this involves!

It's been discussed before, but I think it deserves repeating here, with the current thread....the display MPG can be much closer to calculated if one does not top off the tank when re-fueling. I find that if I stop fueling when the pump clicks off the first time, I am almost the same on both methods of determining MPG. Also, as we all know, the hand calculated method has many inconsistancies as well. Different temperatures when fueling, slight slope of the car when fueling, different pumps at different stations...etc.

With all this said, I am interested in seeing what the poll determines. At first I calculated each tank, but now, after 30,000 miles, I am getting lazy, and just asume 1MPG less that the computer tells me, and I am extremely happy! This gives me about 39MPG over the 30,000 miles, just about double what the "old" car got.

EDIT: One last thought, It does vary some between the NAV equiped vehicles ENERGY display and the MFD display in the speedo area, as the former is user re-set, and the latter, resets automatically when refueling.

 

I take an average of the MFD and NAV ENERGY screen. I find it is usually within 1.5+/- from a hand calculated so I stopped doing the hand math and started recording the average only. Many times the MFD and NAV are the same. Rarely do they differ by more than 1.0.

Sorry, I failed to pick two choices :-( .... I should read better....

 

As Long as you pick the difference it's ok. If someone picks the difference then they obviously would have chose the hand method.

Now drop and give me 50 push ups for your error sir!!

 

I didn't pick a difference


1........2..........3.....oh my......4.......phew......5........I can't do any more......please.......*collapse*