In Reply to: Re: Oil tested after 10 years use. posted by Tim Daley(MI) on December 10, 2018 at 12:43:35:
Correct, Tim. THe additive package in oil breaks down not the oil itself. As oil becomes contaminated the detergent and corrosion inhibitors are unable to keep contaminants in suspension. The older paraffin based oils left thick deposits in the engine as the oil degraded, partly as a result of open breathers and incomplete combustion of gasoline. Modern cars with closed systems and computer controlled fuel delivery systems don't have that problem.They burn a lot cleaner and oils are exponentially better than lubricants of twenty years ago.
I sampled the oil a couple of times a year in my truck engines. Same for any used cars I bought. Sixteen bucks per sample which gives the PPM of all the metallic elements in the oil and and the OMG limits, along with any evidence of anti-freeze intrusion. NAPA does sampling as does CAT