engine oil

[daver clasper]

Hi everyone

Something Iv'e pondered for years

I can see why oil need changing due to mileage but not time (12 months seems to be suggested).

After all, is it not billions of years old anyway.

Any advice please.

Cheers, Dave

[Steve AKA vitessesteve]

I have heard it said that oil in a sealed can will keep whereas once the oil is free to evaporate and oxidise it starts to age.

[GT6 M]

well put it this way.
Yer engines a bit worn, you got blowby into crankcase.
so ye done 1000-2000 miles, year oil is black wid sheite frae combustion.
not to mentionee the condensation that can get in with short trips.
never heating up to boil the conden off.
all this adds up to an acidic mix.

leave that in year engine standing, it cant doo too much good

M

[heraldcoupe]

It's the fungus that grows in used oil...

[RobPearce]

Quoted from Spitfire6

the microbes will "eat" the oil and synth the HC into sulfur. HC4 - O2 = S.

No, that's chemically impossible. There is simply no way to react a hydrocarbon with nothing to produce anything other than hydrogen, carbon or another hydrocarbon.

The microbes digest something else in the oil, not the hydrocarbons, if they're producing anything with sulphur in it. Hint: there are impurities in the oil - that's why some rather purer oil is labelled "low sulphur".

[JohnD]

If you have ever dismantled an engine that is clogged with "Black Sludge" you know it is a good idea to change the oil.  Sludge happens in neglected engines and is a compound of carbon from blow by, the acids mentioned above breaking down oil and metal wear particles so fine they dry to dust.  
Another way of breaking down oil is that the molecules get shortened.  It's the length that gives the lubricious and viscosity, and use breaks the molecules so that the oil is less good at its job.

You can buy cheap oil and change it frequently, our expensive with lots of detergent and other additives to prolong its life. Your choice!
John

[Clive]

Every Triumph engine I have taken apart that has not been apart before (or for many years) has had a layer of black sludge in the bottom.
I suspect this was normal before high detergent oils?
If you then stick a nice quality modern oil in there is a danger that sludge will break up and go around the engine
I am a fan of cleaning sumps out, I really believe it helps with the longevity of the engine. And is easy to do especially if the engine is out anyway, ie if fitting a used engine. The danger is you then start taking bearing caps off.......

[ferny]

So, hang on. I can't put orange juice or mushrooms in my engine oil?

[JohnD]

Prunes, Tony, prunes.
J

[GT6 M]

The microbes digest something else in the oil, not the hydrocarbons, if they're producing anything with sulphur in it. Hint: there are impurities in the oil

I no what it is, its their Sheite, Sheite really stinks at times.

Ohh and talking aboot Microbes,  ye wanna see what they doo to a boats deisel system,  orrid  mess it gets.

M

[thebrookster]

Quoted from GT6 M

Ohh and talking aboot Microbes,  ye wanna see what they doo to a boats deisel system,  orrid  mess it gets.

M

NO I BLEEDING WELL DO NOT WANT TO SEE THIS!!

We have been having a mild case of this on my current ship, driving us all up the ruddy wall!! There are plenty of additives you can buy to prevent these issues with diesel fuel (though trying to convince our company of this is proving slightly difficult lol), makes me wonder if there is something available for lube oil as well??

Cheers,

Phil

[JohnD]

I knew I had it somewhere, just couldn't find it.
THE BLACK GUNGE!

In the TOP of an engine I bought recently for stock.
AS the rockers are like this, can you imagine the sump?
An inch of GUNGE so thick it wouldn't drain out of the plughole.
Probably as carcinogenic as cigarettes, and very difficult to wash off!
Nasty, nasty stuff.
JOhn

[RobPearce]

Quoted from JohnD

An inch of GUNGE so thick it wouldn't drain out of the plughole.

Years ago a friend of mine related the tale of when he first bought his Triumph 1500 (FWD). He decided after a few days that an oil change would be a good idea, so he put it on ramps and undid the drain plug. Or was it? No, he must have made a mistake, because he'd taken that plug all the way out and nothing emerged. Check the workshop manual. Well, it certainly looks like the plug that shows, and there doesn't appear to be any others but that hole is dry. Poke in a finger... eurgh! Black sludge!