Saw the light -> My 1986 AE86 project

[Mux213]

Andreas,

Reasons I've heard about but haven't got any experience with are indeed mostly related to filth in the mineral oils that have gotten stuck in the engine coming loose due to the cleaning additives in the (semi) synth oils.

They could clog the filter but worse yet, as 'larger' piece come loose they can clog the smaller oil canals in your engine and slowly destroy your engine.

Also I've heard stories of engines with old gaskets that only still keep the oil in due to the filth collected in those gaskets, once the filth gets cleaned up by the better oils, the gaskets come apart and your engine starts leaking oil.

These offcourse are nightmare scenarios for which I do not know if they are likely or very unlikely and in what respect these are myths.

What I do know is that damaged and wear already done to your engine in its lifetime isn't undone by using newer oils so I really don't see much reason to switching to a much more expensive synth oil compared to a good quality mineral oil. Using mineral oil doesn't introduce new risks.

It is difficult to say now that the improvement in your engine is purely subjective or is due to the simple fact the old oil wasn't all that good to begin with and a similar effect would have been reached with a good mineral oil.

Synthetic oils are thinner and that can also cause some improvement as there is less resistance meaning a nicer reving engine, but again, keep in mind that with an old engine thats always run on mineral oils, clearances are far from factory and using thinner oils will only heighten the risk of trouble down the line.

Off course after a fresh rebuild of your engine, the story changes completely... I would always run a freshly rebuild engine on synths, here there is a definite difference between mineral and synth. Using mineral oil for rebuild engines could result in your newly build engine just wearing down quicker (all though I have heard of people using mineral oils for the brake-in of their engine because of that reason and because you don't rev a freshly rebuild engine anyway, then change to synth after brake-in, also saves you $$$).

(keep in mind, the above is my opinion after a lot of reading, but way to little practical experience, so I could be way wrong )