I’ve been promising updated maps for months, and here they are. You can see my other maps at this page, Please see the following posts for more details about each map.
The final mileage is as follows (based on the trip calculator at http://www.distancescalculator.com/):
Miles traveled in the Impala by season:
Total mileage for the first 8 seasons on the Impala: 178,282.
However, in season 1 we see the Impala’s odometer, and it has 70,098 miles showing on it in. If we subtract the known mileage from before that episode, when Dean first visited Sam at Stanford, his odometer probably read somewhere near 58,081, for a total of 236,363.
But the odometer on the Impala only has 5 digits, so we have to assume that it has turned over a few times, with John and Dean driving it for hunting purposes since 1984.
If we average the mileage per year we get a mean of about 22,285. If we assume that kind of mileage since 1984 (minus a few years for things like Dean parking it in Indiana for a year, etc.), the Impala probably has around 534,846 miles on it. Give or take. And this is just known highway mileage, not including driving within cities.