Best oil for a BX diesel.

[Mothman]

I'm with David on this, Diesel engines will produce more soot/carbon deposits (which is why their engine oil goes black so quickly after a change).
This carbon floating around in the oil will cause premature wear if left in there too long.
Just on that basis alone, I'd rather use cheap oil, and change it more often.

As a layman, how much damage does carbon do to the engine? I thought it too was pretty slippery stuff?
I can understand if it builds up in large chunks ie in days past a decoke was a regular need but with all the detergents and additives in todays oils isnt it kept in suspension within the oil?
I only do about 3 k a year so i change the oil only once a year.

Andy

[DavidRutherford]

As a layman, how much damage does carbon do to the engine? I thought it too was pretty slippery stuff?

It is and it isn't. Compared to long chain hydrocarbons, carbon on it's own is not as lubricating, and does indeed lump together a bit and create particulates in the oil.

The main reason for changing the oil often is that the nice long-chain hydrocarbons that provide lots of protection for the engine get chopped up pretty quickly by things like the pump, piston rings, cams and followers etc, and end up a fair bit less lubricating. Doesn't matter if the oil cost £5 for a sumpfull or £50 for a sumpfull, it still gets chopped up and becomes less lubricating. Chemical degradation of oil can be reduced, but mechanical degradation is far harder to reduce.

XUD engines are a product of 70's production methods (remember, it was first introduced in early 1982) and consequently do not need sooper-dooper low viscosity oils. In the 70's the standard oil change for most cars was 3000 miles. The XUD is not really very different.