Oil and what else counts as well as ZDDP

[Barry]

The ZDDP dosage in API SM rated motor oil has been reduced from 1000ppm to 800ppm due to the fact that it contaminates Catalytic converters. API SL rated oil can still have 1000ppm and that limit was in place for approx. 20 years going all the way back to API SJ spec so it’s a long time since there were higher levels than 1000ppm in normal Motor oil. In spite of this many claim that at least 1200 ppm is needed for all flat tap engines.

There is a popular generalisation that all old engines have flat tappets and so need 1200 ppm of ZDDP while all modern engines do not as they have roller followers. This in my view has to be nonsense. Not all modern engines have roller followers and many became even more demanding of their oil rather than less when they left pushrods and tappets behind. I remember the early Ford pinto OHC engines wearing their cams out and then there was the Honda V4’s to name only 2. The classic recent example is the Volkswagen Pump Duse or PD diesel which is an excellent engine to drive behind but Volkswagen built in a lubrication problem worse than any airhead has to worry about. The camshaft is given the job of both opening the valves and actuating the diesel injector pumps. This halves the contact area and doubles the stresses. A PD engine can wear the cam lobes out unless fed with the absolute very best quality fully synthetic oil available. So demanding is the oil specification that Volkswagens insists on it’s own oil standards which have become amongst the highest in the industry and worth taking note of when choosing oil. And they still manage to do this without 1200ppm of ZDDP in the oil.

So lets not be airhead martyrs where oil is concerned. There are some other very demanding engines about.

In choosing oil, first we should consider that ZDDP is a surface coating providing boundary lubrication that is only needed when the normal oil film (hydrodynamic lubrication) breaks down. So we need to consider what aspect of an oils specification determines when the oil film breaks down bringing ZDDP into play. The measure of an oils ability to maintain a film in high pressure areas like cam lobes/lifters is called High Temperature High Shear (HTHS).  There is a standard HTHS test which measures viscosity at 150 deg C. This is the main specification to determine the high temperature protection that a motor oil gives to prevent engine parts from rubbing together and then relying on ZDDP to prevent wear. The best quality oils and especially synthetics will have a higher HTHS viscosity than the minimum requirements so they place less demands on ZDDP than lower quality oils. As a result you can’t directly compare oils in terms of protection solely on the ZDDP content.  

The minimum HTHS viscosity standards required by SAE J300 are as follows:-

20W50 must have a minimum HTHS of 3.7cp

15W40 must have a minimum HTHS of 3.7cp

10W40 must have a minimum HTHS of 2.9 cp

If you can find an oils HTHS specification obviously choose the highest but if not and you want to use a thinner oil in moderate  climates any good brand of 15W40 is going to be reasonably safe bet in respect of HTHS compared to a 20W50 as they both have the same minimum HTHS requirements.  This is why I’ve always been happy to use a good dual rated petrol/diesel 15W40.  With 10W40 on the other hand you have to be more careful and make sure to buy a quality oil with a higher than minimum HTHS which usually means at least semi synthetic.

As I’m in a moderate climate and in addition my engine runs particularly cool I’ve decided to go for 10W40 this year.  I’ve chosen to use Valvoline Durablend 10W40 which is a 30% synthetic dual rated Petrol/Diesel oil that meets API SL/CF,  ACEA A3/B4 and Volkswagen 505.1 specs.  The SL spec means ZDDP can’t be above 1000ppm but ACEA B4 includes a much tougher test for cam wear than the API standards so that’s a good plus point and so is the fact that it meets the Volkswagen spec.

To make life simple I can also use this oil in my car as it meets the Mercedes Benz 229.1 spec.

[Speyman]

Barry,
I just saw your very informative text on oils. I drive a PD Jetta TDI and the only 505.01 spec. oil available here comes from the VW dealer, Castrol SFX OE, if I recall correctly. I have speculated how appropriate it might be for my 1981 R65.

Your post mentions 505.1. Is that correct or did you mean to type 505.01?

[Barry]

Speyman

You are correct  505.01 is the spec suitable for some PD engines although there are 2 higher specs  506.01 for extended change intervals and and a 507.00 for later engines with particle filters.

My oil met the older 501.01 and 505.00 specs which I thought were good additional indicators of quality.  I guess 505.01 would be suitable for an airhead provided it could be found in a viscosity right for the operating temperature but 505.01 seems to apply mainly to 5W40 oil so that would only be suitable for cold climates. On the other hand I'm using 10W40 and it's only the 40 bit that counts for engine protection so maybe I would use it.  It depends on the actual viscosity and HTHS.
40 is a range so it could be anywhere between 12.5 to 16.3 cSt at 100 Deg C. I'd want to look at the actual published figure to make sure it wasn't right at the bottom of that range.

[stup9876]

Noticed gulf 20w-50 in a local garage for 16 quid its API CD/SF so should be OK anyone got an opinion (branded oil of acceptable quality or higher spec but by lesser makes comma,car plan etc)

[Bob_Roller]

I've been using motorcycle specific oils since around '83 .

The motorcycle specific oils are higher in the components that tend to be beneficial to motorcycle engines .

My first motorcycle, a '79 Yamaha XS400, I used automotive oil in it and had cam lobe damage in less than 8,000 miles .

Convinced me to use motorcycle oils after that .

I don't put enough miles on the bikes to go to full synthetic, I change the oil and filter at least once every year on all the bikes .

[Justin B.]

I have been switching to the Valvoline VR1 racing oils in both conventional and synthetic.  They proudly boast of higher zinc/phos levels.  From their data sheet it shows:

Zinc/Phos (a weight percentage I believe) - .14/.13

The only caveat I read was not to use in wet-clutch applications...