Oil sample analysis?
The metals portion is better understood with several analyses over several oil changes but even on the first oil analysis you can get quite a bit of information. They''ll check for antifreeze in the oil as well as diesel & water. They can also check the acidity of the oil. All of these give reasonably clear hints toward problems the engine may have or how the owner maintained the engine. For the cost on an oil analysis ($25-$35) it''s one of the cheapest & best ways of looking inside the engine without having a formal engine survey done. Ask the lab what they can tell you with a look at the oil...lots.