Originally Posted by RonMaiden
I'm partial to synthetic in engines that see severe duty and I would only use synthetic in a turbo aplication due to the extremely higher heat temp from the engine to the turbo and of course low temp pourability is a biggie on start-up. My vehciles don't get too many miles a year on them like they used to so I just change my synthetic oil once a year no matter how many miles I put on it.
Is that following the recommended drain intervals of the oil company that manufactures the oil in question? A mere handful are safely capable of extended drain/elapsed time intervals. Most are not safely capable of that rigorous service.
Oils have a recommended change interval based on mileage and also elapsed time
, whichever comes first. With an engine that even only gets a few hundred miles per year, as that oil just sits in the engines crankcase with the engine not even running, it is going through chemical changes from blowby gases, temperature changes, fuel in the oil, humidity/water, etc., that degrade the performance/protection ability of the oil. For this reason, low mileage/short trip driving where an engine doesn't get up to normal operating temperatures to evaporate water and fuel inside the crankcase can be some of the most extreme conditions for an oil to try and contend with and immediately falls into the severe service
category. It might, "look okay", on the dipstick, but actually be in terrible chemical condition. If the oil isn't formulated to withstand a long drain interval in elapsed time and it isn't drained by the manufacturers recommended time schedule, engine damage can result. Be careful and check to see if the oil you are using has a recommended change interval up to a year in elapsed time. Just go to their website and search using Keywords --> Recommended oil change interval.