I also have my doubts about it's acuracy it's probably withing +/-10mph, also the frontal area of the car may be the same as a blocky square nose car, the shape of the frontal area is a big factor. such as a flat front end like in 60's muscle cars vs the sleek aerodynamic shape of the crossfire's swooppy nose and windshield. there are many more factors you can add to his exel formula to make it much more acurate, but I think it's close enough.