Most cars and trucks today don't need to be warmed up from a a drive-ability stand point. It's my belief that it is done for cabin heat, just as in the south they are left running to keep it cool. While we can't determine how much wear is created by the fuel enrichment and additional running time there is obviously some. Just as which engine has more wear a lower mileage car driven in the city or a higher mileage car driven on the highway.
Is oil dilution reduced in modern vehicles absolutely, I'll bet the management system doesn't forget to remove the choke (an antiquated method of fuel enrichment by reducing air flow.).
