learn to take better care of your engines. I tore down a propane powered 454 with 160,000 miles w/ conventional oil and it was so clean you can eat off of it. my last 440 with granted only 66000 miles gas powered same deal.
And do you know why the 454 was in such good condition? It runs off of propane. Propane runs much cleaner than gas causing less problems for your oil as blowby occurs.