More Math Mayhem

[Glen Baker LLC]

So do you think it was the tire/rim sizes that made the difference?

Yes, I think it was.

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[Mavster Mechanic]

[QUOTE="Mavbollover point for MPG?

There is no rollover for MPG. That is a continual calculation based on the miles counter and the gallons counter. The only "rollover" would be when the miles resets to 0 at 10K miles and I presume there would be a reset on the gallons, perhaps at 1,000 or maybe 10,000 gallons.

The two mpg figures would never become equal if you leave the two trips continue to run because the first one would always have the extra trip towing in it to account for. Mathematically, the two would continually become closer to each other but never the same.
[/QUOTE]
And I am saying that is how is should be.

And I am also saying it may not work like that. Most people don't care to put it to the test. So I will. But it will be a multiple month long process.

 

[Joe Strummer]

No, your calculations are unweighted. The towing trip used almost 2.5x as much fuel and should receive 2.5x the weight.

The total trip used 97 gallons in 2273 miles. How is that not 23.4 mpg?

My calculations are weighted by milage.

 

[KenE]

It would be interesting to calculate it by hand if you knew how many gallons total were used. I wonder how close (or far) it would be to the # the truck displayed.

EDIT: I calculated all of this by hand and got 23.37 MPG. Somebody let me know if my thinking is off but I think this would actually be the way to do it.

First drive: 1063 miles at 15.5 MPG = 68.5806 Gallons

Second drive: 1210 miles at 42.2 MPG = 28.6730 Gallons

Round trip fuel usage: 68.5806 + 28.6730 = 97.2536 Gallons

Final MPG: 2273 miles / 97.2536 gallons = 23.3719 MPG

So, this leads me to believe your truck's trip 1 result at the end of your round trip is correct.

This is correct, basic math.

 

[HeyBales]

There is no rollover for MPG. That is a continual calculation based on the miles counter and the gallons counter. The only "rollover" would be when the miles resets to 0 at 10K miles and I presume there would be a reset on the gallons, perhaps at 1,000 or maybe 10,000 gallons.

The two mpg figures would never become equal if you leave the two trips continue to run because the first one would always have the extra trip towing in it to account for. Mathematically, the two would continually become closer to each other but never the same.

The calc's keep the average going past 10K - at least for my last oil change that went over on Trip 2.
Here we have going into winter, and highway speeds for a trip - wonderful double combo.
Ya, the 38.2 was after the trip. The 37.8 was after some very cold snaps.

I've experienced what others have posted seeing, regarding the MPG used for the DTE.
That has a shorter range, not decide what though.
You get done with a long highway speed trip and mileage down around 30 mpg and corresponding DTE, and if you don't have to refill, then your next couple weeks of better city mileage slowly has the DTE increasing as old low mpg is replaced with higher mpg figures.
That has happened within the space of a tank - so not sure if last 200 to 400 miles rolling avg.

Had it go the other direction too, long highway speed trip - DTE looking pretty good at the start. After a decent chunk of miles that DTE has dropped a good amount.

 

[Chops]

You need to account for mph.

For example, drive 100 miles at 50mph, turn around at drive back at 100mph. Your average mph is 66 not 75.

If you drove longer (time) at 15 mpg than at 42mpg - the average will be skewed more towards the 15mpg. Bring a stopwatch next time


Edit - like matmoto said, divide total distance by total gallons used for the mpg. Seems your computer was spot on yay.

 

[dochawk]

my new house was built as 2,000 sq ft, and later got a 750 sq ft addition, for a total of 25,000 . . .

House 250, Math 0!

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