In Issue No 333 February 2009 of the Rover Sports Register magazine "Freewheel" there is a fascinating and informative article about lub oil. It is submitted by the Castrol Technical Centre, so of course, they only mention Castrol branded oils. But the technical content is extremely informative.
To summarise, old fashioned engines are built without modern surface hardening techniques and with inferior tolerances to modern engines. Plus they don't have catalytic convertors. They were therefore suited to oils with a reasonably sticky cold viscosity with, in particular, lots of anti-wear additive - notably zinc dialkyldithiophosphate (ZDDP). Modern oils have a very low cold viscosity, plus their anti-wear characteristics have changed markedly because ZDDP reacts with cats and is therefore virtually eliminated. Also modern oils tend to have lots of detergents.
The thrust of this is that engines of our era are likely to have much higher wear rates on modern oils - especially on start up and cold running, plus the detergents in them are liable to cause carbon build up to detach from the engine and block oil ways.
Castrol therefore market a range of oils to suit our era of vehicles with low detergent and high ZDDP. IN particular their Castrol XL20W-50 looks to be most appropriate for the P6, both 4 cyl and V8.
If you'd like a copy of this article I can scan and e mail for you.
Chris
To summarise, old fashioned engines are built without modern surface hardening techniques and with inferior tolerances to modern engines. Plus they don't have catalytic convertors. They were therefore suited to oils with a reasonably sticky cold viscosity with, in particular, lots of anti-wear additive - notably zinc dialkyldithiophosphate (ZDDP). Modern oils have a very low cold viscosity, plus their anti-wear characteristics have changed markedly because ZDDP reacts with cats and is therefore virtually eliminated. Also modern oils tend to have lots of detergents.
The thrust of this is that engines of our era are likely to have much higher wear rates on modern oils - especially on start up and cold running, plus the detergents in them are liable to cause carbon build up to detach from the engine and block oil ways.
Castrol therefore market a range of oils to suit our era of vehicles with low detergent and high ZDDP. IN particular their Castrol XL20W-50 looks to be most appropriate for the P6, both 4 cyl and V8.
If you'd like a copy of this article I can scan and e mail for you.
Chris
