I'd use it, but then I'm in Taiwan, where it never gets close to freezing. (Postage would be too expensive, I suppose)

Shouldn't be a disaster in the UK, but your initial lubrication on cold startup probably wont be quite so good as with a multigrade. Maybe use it as a "summer-only" oil?

OTOH hand your shear stability will be better, but since the stuff is free, you can change it as often as you like, so that isn't much of an advantage.

Might be worth finding out how much ZDDP anti-wear additive the oil has, if you can. I dunno if big marine diesels have flat tappets (I'd guess not) but if your VW has, you might need the zinc protection.

If it is actually free in unlimited quantities, you might perhaps consider using it as fuel?

Edited by edlithgow on 02/03/2013 at 10:10

Sorry Focussed, it's the crosshead type engine that separates the cylinder from the crankcase by means of a diaphragm with a mechanical stuffing box (The older type of crosshead engine like the Doxford LB had no diaphragm and a foul crankcase!!) The trunk type engine resembles more closely the automotive type engine.

The current trend is towards reducing Sulphur content (and indeed eliminating it in coastal waters) in marine fuels - with the attendant lubrication problems - which brings us neatly back to the original question - I personally would not use it both on viscosity grounds and the fact that (most) reputably operated marine engines are run under a far stricter oil filtration, purification and monitoring regime than any automotive engine.

If you must use it then I would reduce the change frequency down to 3 or 4 thousand miles (Which is what it was with the older generation of mineral oils anyway!!)

If the oil has more detergency than the recommended oil (unlikely) then there may be an additional risk of dislodging existing carbon build up in the lubrication system with the attendant bearing and turbocharger damage.