You can use, for example, the following data:
0 0
1 60
2 120
3 180
4 240
5 300
6 360
7 420
8 480
9 540
10 600
This data represents a function of:
y = 60x
Which means that the car travels 60 miles per cad gallon.
This distance traveled per gallon is greater than the distance traveled by Mr. Miller's car.