TECHNICAL BULLETIN NO. 169
AUGUST 2010
ZINC MYTHS AND LEGENDS 2010 UPDATE
There have been a number of articles and we have heard comments from various “expert”
commentators regarding the more recent API specifications and their impact on older petrol engined
vehicles. Unfortunately there is a lot of mis-information out there and also contradictory information as
to what can and cannot be used in older vehicles.
The focus has been on zinc, or more correctly, ZDTP (zinc di-thiophosphate). For many years this
has been the anti wear additive of choice as it is the most cost effective (and one of the most effective)
chemistry to use. Also incorrectly described as an extreme pressure additive, its primary role is to
prevent wear in the rings and in the valve train (cams, tappets, valve stems etc) of the engine.
When you add ZDTP you also add phosphorus. This is a catalyst poison and there have been limits
on it since the days of API SH (1994) when a 0.12% (1200ppm) limit was imposed. Prior to that, in the
days of API SG (1989) many manufacturers already had put a 0.10% (1000ppm) limit on phosphorus.
So, “low” phosphorus has been with us for quite some time.
In effect, an engine oil that contains about 1000ppm phosphorus or higher, will easily provide the
required anti wear properties for older engines.
The step from API SH to API SL was accomplished by a combination of new additives or adding
additional anti wear and anti oxidant to existing blends. As an example, the Penrite HPR petrol oils
and Pro upgrades from API SJ to API SL required the addition of these components to pass the
relevant engines tests. These were not phosphorus based, but used organic molybdenum additives
(not molybdenum disulphide – we do not recommend that for any engine), to keep phosphorus levels
at 1000ppm. Many other companies followed similar routes but there was certainly no loss of
protection, even if they started from scratch.
Now we have API SM – for the first time, the limit on phosphorus is from 0.06-0.08%. (600-800ppm).
There are industry concerns about the applicability of these oils in older engines. However, the limit
only applies to 0W-20, 0W-30, 5W-20, 5W-30 and 10W-30 oils (so called “ILSAC” grades). Any other
grades are exempt from this. When HPR 10, 15 and 30 initially went to API SM technology, they
maintained their phosphorus levels of about 1000ppm (about 1100ppm zinc). None of the viscosity
grades for these products are bound by the 800ppm upper limit.
Therefore blanket statements about API SM oils will be incorrect and further research will be needed
by the end user. API SN has the same limits and ACEA C1 to C4 are also low zinc oils.
There is one other factor with non-ILSAC oil grades. If they also have the European ACEA A2/A3 with
B2/B3 or B4 performance levels, phosphorus levels will also be at 0.10 % to 0.12% as their tests have
been more severe than the API for some time. Hence an oil that is SL (SM)/CF/A3/B3 also well
exceeds the anti-wear requirements for older engines.
The irony is that API SF and SG oils formulated in recent years usually have phosphorus contents of
around 0.08% (usually 0.1% maximum) anyway due to other advances in technology, unless the
blender chooses to add extra additive.
Currently, our traditional HPR 30, 40 and 50 products are all high zinc. In fact there is no HPR grade
(petrol, gas or diesel) with a zinc level of less than 1200ppm, regardless of its API rating.
We also have range of oils (Shelsley, Classic, Heritage) that are designed specifically for pre 1970
motor vehicles.
This brings us to diesel oils.
Currently, there have no phosphorus limits outside of grades that are API CJ-4 or ACEA E6 (which
have limits) – as such many people recommend them for older cars, even though many others say
that the detergent levels are too high and the engine will use oil. Well, you cannot have it both ways.
This one originated from the USA and hence did not take into account European ACEA A/B standard
petrol engine oils, which are easy to find in Australia, NZ and Europe, but a lot harder to find in North
America.
Yes, the engine may use oil, but only until the cleaning period is complete – unless you are unlucky
enough to move a deposit that is stopping oil leaks that is. However, an engine in good internal
condition will run quite happily on diesel oils as long as the SAE viscosity is correct.
This leaves Synthetic oils. Many people say they are too “slippery” for older cars, and can cause wear
and oil consumption. Well, wear protection has little to do with the base oil type and everything to do
with the additive (all else being equal). If the wrong anti wear additive is used (and this did inflict a
brand of synthetic oil not that long ago) then it does not matter how good the rest of the oil is, wear will
occur. Hence, the right type of synthetic oil is quite OK in an older car, but unless it is fully
reconditioned and then correctly run in, then there is no real benefit to the end user. It is true that
synthetic oils (especially the PAO type) have lower friction, as their chemical structure allows the
molecules to slide over one another more easily than a mineral oil, but if the correct additives are
used, then this becomes a benefit, not a detriment.
The choice of the correct oil for older cars comes down to various factors such as:
Original Viscosity Specified
Condition of engine (leaks, sludge)
How often the engine is run
How the vehicle is to be used
Oil consumption
Current oil used
Blanket statements are not useful to anyone, be it the vehicle owner or the oil industry. If you have
any doubt as to what oil you should use, contact your preferred supplier – preferably Penrite of course.
On our web pages (
http://www.penriteoil.com" onclick="window.open(this.href);return false;) are listings for both post 1970 vehicles and also another
section for pre 1970. In both cases, we have chosen the correct oil in our range that would suit the
vehicle shown, basis the condition we would expect the vehicle to be in and how we expect it to be
operated.
Information in this bulletin is correct at August 2010.
; daca afla cineva, sa-mi spuna si mie.
