I always work with the concept of "if in doubt change it out".

As for engine oil analysis. Yet another thing from the aircraft industry that has come to cars that really does not do anything for you. Unless your really familiar with the engines and the way they are "supposed" to wear and familiar with a fair amount of metalurgy the pretty printout you get is pretty useless. What exactly can you do to stop your engine from wearing out? More frequent oil changes might make you feel better but its not going to slow the process much when you have a problem of some sort. The only thing thats going to change things is "going in" which in all reality will probably cost very close to an engine overhaul or used engine. In some cases your better off by just waiting for the engine to fail and then go in to see what happened in there.

In private aircraft oil analysis is used to determine engine overhaul times. Many owners will start doing oil analysis when they get near their TBO time to determine how far they want to go before biting the bullet on an overhaul. Many owners will go over their TBO time based on the oil analysis. In a plane oil analysis is useful because the engines are so critical. No one is going to die because their engine blew on the expressway but if your flying over cities or water and your engine goes your in bit of a pickle and you better hope there is a nice open field within gliding distance. WIth aircraft engines there is a weath of data that will can actually tell you what your analysis number mean. With a car there is no such data. So if your suddenly seeing a lot of aluminum in your oil your only answer to the problem is really just an educated guess that may just be part of the engine's normal wear process.