Depending upon the base stock,,,poaos are not much higher than gpII dino oils and the pao leaves harder deposits. I have read stickers placed be the pyrometers on many semis "non cooled with out electronic management " not to shut off the engine unless the exhaust gas temps are 300 F or below. So if you run a syn oil that cokes at 700f and the egt is 1,100f and the engine is shut off what will happen? the numbers are made up and to get the exact numbers do a search but in general I hope you can get what I am getting at. I am not knocking syn oil but the dino is very good and I would do the free oil changes to flush out the wear metals. Also there are manufactures that recommend syn oil for what ever reason needed ,so if syn was really needed the mfg would recommend or require syn oil to cover their warranty claims'.