Many of the vehicles listed for sale that have high mileage often say it is mostly highway miles. Does this make a difference in the life of the vehicle? When you ask a tech it is like asking them which oil, tool brand or blonde brunette or redhead they prefer. It does cause less wear and tear on the doors and the interior and the brake system but as far as the engine goes there are several factors that come into play. Cold starts are when most of the engine wear occurs but synthetic oil eliminates a lot of this wear. Also the service or TLC in general the vehicle has had plays a major role in the life of the vehicle. Most drivers that put on a lot of miles tend to take better care of their vehicles as they want them to last and a breakdown would cost them valuable time. So it would play a role in the purchasing decision but many other items should also be considered. Cars with high mileage are usually used in business so most of the expenses are deductible and the owner should be able to provide a record of service. I tend to buy a car a I like and live with the repairs, my Bonneville has a new GM engine that runs great but the rest of the car is having problems, water pump, alternator, wheel bearing Etc. My is presently looking at a 2005 Bonneville and it is a nice ride, thought she wanted a SUV but she likes the Pontiac.