interesting thread link from bob the oil guy
https://bobistheoilguy.com/forums/ubbthreads.php/topics/3973205/Castrol_Australia_and_ZDDP
quote ...
" However most oils from the 1950’s and 60’s had lower Phosphorus content than even the latest passenger car engine oils, i.e. it was typically 0.06% which is even lower than the 0.08% limit set by API SM.
ZDDP is a multifunctional additive; it has powerful antioxidant effect in addition to the antiwear characteristics. The size and type of the alkyl group attached to the Thio phosphate within the molecule influences the relative antiwear antioxidant balance of ZDDP additive. Over time Castrol have used modified ZDDP’s that are more intended for wear performance and substituted other materials to boost antioxidant performance of our engine oils. So looking at Zinc and/or Phosphorus levels alone does not tell the full story in terms of wear protection.
There has been discussion about using diesel engine oils instead of passenger car engine oils. Some of these do currently contain higher levels of Phosphorus, ZDDP, than passenger car qualified to API SL or SM. They have higher Phosphorus to help minimise soot related wear.
The higher level of Phosphorus is not a guarantee of satisfactory wear protection. As I said earlier, wear performance is related to the particular ZDDP being used. Also many of the diesel oils with higher Phosphorus also contain higher levels of detergent and dispersant which compete for surface area with the ZDDP which can reduce its effectiveness. During the development of the current API SM engine tests, a high phosphorus diesel engine oil was run in a flat tappet, push rod engine test and it failed the wear requirements with worse results than most low Phosphorus passenger car oils.
The first few minutes of operation for new cam and tappets are very important. Run-in is important for good long service life. Castrol have put considerable effort into understanding valve train lubrication. Research has shown one of the highest if not highest wear mode for a cam and tappets is while the engine is at idle. Running an engine at medium speed, say 2,000 to 4,000 rpm generates much less metal-to-metal contact between cam and tappet than at engine idle.
When running in new cams and tappets avoid idling as much as possible in the first 30 minutes to hour of operation. Make sure the cam and tappets are pre lubed with Moly grease and oil. Try to keep engine oil temperature above 80°C. Driving the vehicle or running the engine under load achieves that most quickly. The cam and tappets should be run-in by 250 to 500 km.
Also ZDDP is temperature activated so running the engine at low oil temperature also accelerates cam and tappet wear.
If a full synthetic engine oil is preferred then our Castrol Edge 0W-40 or Edge Sport 10W-60 is recommended. Again these are formulated to 0.10% Phosphorus maximum and can be used with flat tappet followers with confidence the same as Edge Sport 25W-50."
