Matt M.

asked • 02/08/16

Mpg to l/100km conversion, fuel economy problem?

We have two vehicles
A:old truck that does 17 mpg (13.84l/100km)
B:old car that does 47 mpg (5.00l/100km)
We are looking to replace one of these vehicles with a new one (of the same size)
C: new truck 19 mpg (12.38l/100km)
D: new car 61 mpg (3.85l/100km)

So which vehicle should we replace to save fuel? The old truck or the old car to end up with.
1). AD (old truck+new car)
2). BC (new truck+old car)

Read bellow once you have your anwser:

The way I solved this:
A:Old truck 13.84l/100km + D:new car 3.85l/100km = 17.69l/100km,
B:New truck 12.38l/100km + C:old car 5.00/100km = 17.39l/100km
Combination BC uses less fuel.(0.31l less)

Now using mpg:
Making the combination AD a better choice.

Why the exact opposite answer? What am I missing here?

1 Expert Answer


Amanda R. answered • 02/08/16

New to Wyzant

Math and Science by a certified TN teacher and homeschool mom

Matt M.

So if the question is what combination of vehicles saves us more fuel? What is the answer? Or is the question wrong in the first place? If so what wold the right question be?


Amanda R.

Since you want fuel economy you would want to compare numbers that show the fuel usages to get the most direct answer.  You could also convert the mpg values to gallons per mile.


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