Alice, absolutely a non valid calulation. Age will not equal mileage unless number of vehicles is considered. Eliminate non diven (museum quality) cars and then list driven vehicles with your formula. I.E.
2003 SRT 10
1997 GTS
2002 M5
This example takes into considertion a multple Viper owner who has a daily driver. THEN calculate age versus combined mileage, must be single driver who drives all cars, significant or insignificant others or other family drivers do not apply. They have to have additional cars. Your original formula fails beacuse very few Viper owners drive only the Viper, they not only own multiple Vipers but pretty significant daily drivers.
Not to the 46 others who have replied here...I hate to say it but some of these forum topics are getting a little off base!!!!!