More Math Mayhem

[Mavster Mechanic]

Towed almost Max Trailer plus almost Max payload in truck.
Plus it was windy half the time.


Reset trip 1 and trip 2 before starting.

Towed 1063 miles.
Trip(s) said 15.5 MPG.

Reset Trip 2. Left Trip 1 going.

No payload. No trailer.
Drove 1210 miles.
Trip 1 (mixed) said 23.3 MPG
Trip 2 (light wt) said 42.2 MPG.

What do you think my 2273 mile average should be?

I think it should be 29.7 MPG.

Another data point.
Same not reset meters.

1063 miles at 15.5 MPG
2059 miles at 43.0 MPG

What is the average?
Truck says 26.8 MPG on never reset Trip 1 that had the towing.

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[Joe Strummer]

29.7 is correct for the trip as you described it. Just a weighted average of your out and return MPG.

 

[matmondro]

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.

 

[DS_Ohio]

I came up with 23.3 and 26.8 mpg.

 

[Howard]

Matmondro's analysis is the correct way to analyze it. A simple average of the mph numbers does not take into account the greater amount of gasoline used in the towing trip.

 

[Mavster Mechanic]

My brain and body was exhausted after so much driving in like, 4 days.

I will keep the meters unreset and see when the data overflows. IE runs out of memory.

The two meters should never match but I assume at some point they will.

 

[matmondro]

My brain and body was exhausted after so much driving in like, 4 days.

I will keep the meters unreset and see when the data overflows. IE runs out of memory.

The two meters should never match but I assume at some point they will.

I believe 10k miles is the "rollover" for the trip meters.

 

[Joe Strummer]

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.

I think you are using unweighted inputs.

My calculation is 1063/2273*15.5 + 1210/2273*42.2 = 29.7.

The distances are almost the same. So if you just averaged 15.5 and 29.7 you get 28.9.

 

[Mavster Mechanic]

I believe 10k miles is the "rollover" for the trip meters.

True.
But what is the rollover point for MPG?

 

[Mavster Mechanic]

I think you are using unweighted inputs.

My calculation is 1063/2273*15.5 + 1210/2273*42.2 = 29.7.

The distances are almost the same. So if you just averaged 15.5 and 29.7 you get 28.9.

However, while miles were "almost" 50/50, gallons burned were like 70% / 30%.

So the towing segment is more heavily weighted.

 

[Howard]

I think you are using unweighted inputs.

My calculation is 1063/2273*15.5 + 1210/2273*42.2 = 29.7.

The distances are almost the same. So if you just averaged 15.5 and 29.7 you get 28.9.

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?

 

[Glen Baker LLC]

This Thread reminds me of the recent video from Fast Lane trucks.
Where the two guys, did a MPG test hybrid VS Eco on their 100 mile course.
They both travel the same distance, but yet their trip computers showed 118.4 miles versus 120.4 miles
They made the comment FORD computers aren't good at math.

 

[Mavster Mechanic]

This reminds me of school.

You could have an "A" average for 15 weeks. Miss one paper in the 16th week and get a "C" in the class. Frustrating!

 

[Mavster Mechanic]

This Thread reminds me of the recent video from Fast Lane trucks.
Where the two guys, did a MPG test hybrid VS Eco on their 100 mile course.
They both travel the same distance, but yet their trip computers showed 118.4 miles versus 120.4 miles
They made the comment FORD computers aren't good at math.

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

 

[Howard]

[QUOTE="Mavbollover point for MPG?
[/QUOTE]
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.

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