Cost per mile of gasoline used. You may find that purchasing a lesser expensive gasoline may actually cost you more to use than a more expensive one. If you purchase a gasoline that costs $1.899 per gallon and get 26 miles per gallon, then you may be actually paying more than if you purchased a gasoline that costs $1.929 per gallon but you get 30 miles per gallon. To calculate the cost per mile, take the cost of your gasoline fill up and divide it by the number of miles driven since the last fill up. That will give you the cost of gasoline per mile driven. With this information, you can determine if the lesser expensive gasoline is really less expensive to use. For example:
You purchase gasoline at $3.899 per gallon. You have driven 250 miles since your last fill up and it takes 9.6 gallons to fill your tank for a total of $37.43. You calculate that you got 26 miles per gallon.
To determine the gasoline cost per mile, take the total purchase price of $37.43 and divide it by the 250 miles driven, it cost about $0.1497 per mile for that gasoline. ($37.43/250 miles = $0.1497/mile or 14.97 cents per mile).
Now, let’s say you purchased gasoline at $4.159 per gallon. You drove 250 miles since you last fill up and it takes 8.3 gallons to fill your tank for a total of $34.52. You calculate that you got 30 miles per gallon.
Again, take the total purchase price of $34.52 and divide it by the 250 miles driven, it cost about $0.1381 per mile for that gasoline. ($34.52/250 miles = $0.1381/mile or 13.81 cents per mile).
That is a cost per mile difference between the two gasolines of only 1.16 cents per mile. But multiply that difference times an example of 15,000 miles driven in one year, that is about $174.00 savings by using the more "expensive" $3.899/gallon gasoline vs. the $4.159/gallon gasoline.
BUT, that is based upon your particular vehicle, operated by your particular driving, and that you actually achieved more miles per gallon using the higher price per gallon gasoline. You must carefully calculate the cost per mile for your own circumstances and determine if this is right for you.