I use UOA's for make buy decisions on keeping or buying vehicles at what I call the "turning point" (120-150k miles). Most of the time I am looking for unusual wear metals and coolant. Since coolant leaks are fairly common and go undetected by most people until they do permanent damage, a uoa for coolant is a big help in deciding to not buy or trade in a vehicle that is at the turning point in it's life. I won't buy a used car without a UOA/Carfax/complete check by my mechanic. You wouldn't believe the "duds" I have uncovered for friends when shopping for a used car. The whole process costs aboout $250 and is definitely worth it. After doing this for several years now I have come to believe that 3/4 of the used cars out there have some major repair issue waiting to happen.