Dirk- the irs rate is not "a rate" it is the maximum allowed by the irs to be allowed deductible to the employee (meaning they do not have to pay taxes on it). It is not necc an indication of real world useage and cost.
For instance Emp A) drives a honda civic (bought 5 years old for cash), emp B) buys a brand new decked out F250 super duty or whatever and finances it. Who is going to have the higher cost to own, operate & insure? Emp B.
We pay .30 mile, and our employees are rarely ever using a personal vehicle for anything more than an occassional trip somewhere or errand on the way home.
They already owned the vehicle, insurance etc and the only incremental cost is the minimal gas and wear and tear being put on for a couple hundred miles or so a year.
If we required someone to use their vehicle for company bus all day every day and wanted it to be a nicer vehicle, the we would adjust accordingly or like we do for outside sales staff make it a monthly stipend.