Hertz - What's Mid-Size?

I reserved and rented a full-sized vehicle, and was expecting an Impala, or vehicle of similar size, as identified by the Priceline and Hertz website. I was offered and received a mid-size Mazda 6 (as classified by the manufacturer), which Hertz considers a full size? Although I complained before I took receipt of the vehicle, Hertz stated their classification was "F" for the Mazda 6, and it was a full-size vehicle! I filed a complaint, and Priceline investigated with Hertz, confirming that I was not downgraded, and their rental designation of the Mazda 6 is as a full-size. How can you rent a mid-sized vehicle as a full-sized one?

I rented a mid-size car through a package from Expedia. They used Hertz who are trying to change industry car sizes by making their own classification of a Chevy Cavalier as a mid size. Chevy has confirmed that the Cavalier is a compact. Neither Hertz nor Expedia will take responsibility for the deception that lead to my renting a car smaller than anticipated per auto industry guidelines.

The consequences of this not following industry standards are global and will impact many. Essentially Hertz is expanding profits by using their own rules to classify cars and thereby giving the customer less than should be expected while relying on auto industry standards. This would be like the beverage industry using a 1 litre bottle while describing it as a quart.