Ok If I put my tin hat on I have a theory. All car mfgs, make deals with suppliers, saving a dollar or 2 on any part is a big deal to mfgs. I wonder if the tires that come on dealer vehicles have slightly more grip but wear faster. I have bought several new vehicles and the tires that came on the cars never last as long as the ones I buy to replace them. I know what that sounds like but I also know the suppliers will alter compounds within limits to reduce costs. As an example, Coke-a-cola, is not just Coke, there are parameters that qualify it as "coke". Bottlers will spend money to buy mass flow meters to allow them to produce "coke" that runs on the qualifying edge to get more cases out of the same amount of concentrate. So maybe tire mfgs run more on the edge making mfg tires and they don't last quite as long, but they have good grip so you buy more when they wear out. Ok, where's the Tylenol?