Ray wrote:I thought that oil doesn't degrade as long as you keep it within it's temp limits? I know they have additives, but if it doesn't degrade if you don't overheat it you could reuse it again right? After a good filtering of course. Or am I being my usual stupid self?
Not stupid ray, you're fundamentally correct. But when oil is inside an engine, how can you guarantee the oil does not pass through a location where it overheats? Not a lot, but just a bit of degradation. Oil flows all over the cylinder head, and if some collects on top of a combustion chamber, some of it may have overheated.
Even more important, oil collects particles. Some of the larger chunks are collected by the filter, but a lot of microscopic particles remain in suspension. Media in an engine's primary filters pull out particles as small as 25 to 30 microns (a human hair is 67 microns in diameters). Secondary filters do better — down to 5 or 10 microns — but also add restriction to the flow. But what size particle can damage an engine? One micron particles can wear out things like pistons, rings, and bearings at an accelerated rate.
What's the investment in an engine, even better yet, a high performance engine where some bloke has laboured and poured his heart and soul into building a killer engine for the car he loves. What does a few cans of oil cost? It it worth the risk?
Bottom line, change your oil, don't be cheap or silly.
Racing should be decided on the track, not the court room.
