How many gallons of gas did I use for my trip and what is the formula to calculate it?

Question

Hello,

I just want to ask how my gallons of gas does my car consume if I travel 8.0 miles for a trip of 24 minutes? My car's mpg is 20 mpg. For this trip, it is usually from home to school and I would be using the local streets, not the freeway. Therefore, there would be frequent stops. The usual speed I would drive at is 35 mph. How many gallons of gas am I using for this trip?

And what is the formula to calculate this too? Thank you.

Answer 1

You need to use up enough gas so that when you refill the tank it takes more than a fraction of a gallon. It also helps to do the test when the car is warmed up.

The way to do that is to travel a 100 miles or so from a full tank, then refill the tank noting how many gallons were needed. Finally divide the miles traveled by the gallons needed for the refill. That is your mpg.

Answer 2

Why are you going to school if not to learn how to do things like this for yourself?

The only relevant information here is your miles per gallon, and the number of miles you're going.  

You get 20 miles per gallon, and you're going 8 miles.  So you used 8/20ths of a gallon.  That's 2/5ths.  

But the fact that you mention how many stops and starts you'll have suggests that you don't actually know what kind of fuel economy you will get, which means there is not enough information to give a correct answer.  

You can't get the MPG any other way than to test it.  The easiest way is to restart the trip odometer when your tank is full, then divide the number of miles by the number of gallons the car takes the next time you fill up.