economics of driving

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elodie.gillain@gmail.com - 14 May 2008 17:35 GMT

Dear Forumers,

Say I can choose between two cars. The gas mileage of the first car is
25. The gas mileage of the second car is 30. Let us say that the cost
of gas is 4$ per gallon.

The difference in gas mileage between the two cars is 5. So the
savings if I choose the leaner car is 4$ per gallon/5miles per
gallon=0.8 $ per mile
Am I right?

I greatly appreciate your help.

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Dave - 14 May 2008 17:46 GMT

> Dear Forumers,
>
[quoted text clipped - 8 lines]
>
> I greatly appreciate your help.

Nope. If you are looking at it in terms of cents or dollars per mile, the
first one is about ($4 divided by 30 miles) 13 cents per mile, the second
one about 16 cents per mile. So the savings is about 2.7 cents per mile.

Don't forget other costs though. If that 30MPG car is a different class, it
could be more expensive to register and insure, eating up that 2.7 cents per
mile savings QUICK. Or looking at it the other way, if that 25MPG car is a
different class, the savings by choosing the 30MPG car could be greater than
2.7 cents per mile. -Dave

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Arif Khokar - 14 May 2008 17:52 GMT

> Dear Forumers,

FYI, this is a newsgroup.

> Say I can choose between two cars. The gas mileage of the first car is
> 25. The gas mileage of the second car is 30. Let us say that the cost
[quoted text clipped - 4 lines]
> gallon=0.8 $ per mile
> Am I right?

Think of this in terms of the units you're using. In order to find out
how much a car that gets 30 miles per gallon costs per mile, you need to
do the following:

30 miles 1 gallon 7.5 miles
-------- x -------- = ---------
1 gallon 4 dollars 1 dollar

Take the reciprocal to get 0.13 dollars per mile

Do the same thing for the 25 mile per gallon figure and get 0.16 dollars
per mile. Then the actual difference is 0.03 dollars (actually a little
less) per mile, not 0.8 dollars.

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