Is the Horsepower of a Car Related to Its Mileage?

Motor Trend magazine collected the horsepower and mileage for 32 cars in the 1973-74 model year.  To see if there is any relationship between horsepower and mileage, I construct a scatterplot of the two variables

There is a clear negative relationship between Horsepower and MPG — cars with more horsepower tend to get lower mileage.