Originally Posted by Mitsu_Joe
Well, engine oil is commonly stated to have a shelf life of 2-5 years, that's why they print dates on the bottles.
That's an old one. No one has ever produced any technical support for those stated shelf-lives (some of which are one year, which is about as bare faced as a corporate lie can be) in any discussions on here, but there is plenty of anecdotal and first-principles evidence to the contrary.
Originally Posted by Mitsu_Joe
Probably the conventional oil you use is less prone to oxidation (that mainly gets caused by additives) as its basically just pure oil, especially the SAE40 stuff will be very long-term-stable. Especially in the temperatures you have over there.
That's a new one. I like conventional oil, but I've never heard that it was supposed to be more oxidatively stable than (by implication) synthetic (where that means something), or that oxidation is mostly "caused by additives", or that conventional oil didn't have additives, or that oxidative stability was greater at higher temperatures. I think perhaps that to some extent you are (a) confusing oxidative with shear stability, and (b) just confused.
What I have heard is that, due to its complex makeup, oxidation of conventional oil tends to proceed more continuously and gradually, whereas with synthetic there's none for a long time, then a rather sudden "error catastrophe".
I've seen it claimed that synthetic drains down less, (which would be a reason to use it in this situation), but I've also seen the opposite claim, so I dunno about that.
Originally Posted by Mitsu_Joe
But as I stated from my personal experience, I wouldn't stretch it that long. I've seen "That oil still looks okay!" followed by internal engine failures quite a few times by now, so I became rather careful ahahah
People sometimes post asking for examples of oil-related failures on here, and they mostly come up empty. Perhaps you could detail your experiences next time.
Originally Posted by Mitsu_Joe
The new title of the thread is hilarious on a side note...
Whaddya mean, NEW title? Someone been messing with my OLD title?
Originally Posted by Mitsu_Joe
On the other hand I wouldn't worry too much about slight corrosion, I'd just start it up and let it idle for some minutes (or pull the plug wires and just let the starter do some revolutions if you're super careful...), then drain out the old contaminated oil and put new one in if there really was corrosion.
The surface rust would probabaly disappear after the first couple of crankshaft revolutions.
I "revived" my car after sitting for almost 3 years, changed the oil and put a new battery in, then started it that's it.
Corrosion is quite unlikely on those parts however (unless you sit for years and years...), high quality iron (of which internals have to be made) helps a lot in preventing rust.
My car still isnt rusted out after 30 german winters whereas some fiats/alfas in the 80s already started rusting at the factory. And thats true for about any part on cars, if you want to design it to hold up, it will.
Specifically talking about camshafts: on older cars like ours the crankshafts are made from cast-iron. The surface is hardened even further artificially using induction hardening. This leaves an extremely hard and almost rust-proof surface of the camshaft. Once this surface is worn down after "long long time"
, the cam will wear out quite fastly, also its more prone to rusting...
Yeh, I had a lot of metal in my oil when I first got the car and wondered if the cams had lost surface hardening, but (short of maybe DIY nitriding, which I'm unlikely to try) there isn't much I can do about that.
It MIGHT be possible to rig something to dribble oil directly on the cams before starting, like I did manually yesterday. Hmm...