Neil
McTavish – Australian Automotive Technology Manager Castrol
In
recent times we have been asked by a number of people to comment on using
the latest oils in older engines. Questions have come mainly from car
clubs but also from some magazines, racers and engine builders. The
questions relate to wear performance on flat tappet cams. Please note, all
my comments in this article are about flat (sliding) tappets not roller
followers, a different story.
Firstly
let me remind people, this is Australia not the USA. I have read a number
of articles where the information clearly comes from the USA but you are
left with the impression that it is written about Australia. The internet
can be misleading if the source of the information is not clear.
I
have been in the technical area of lubricants in Australia for more than
30 years. So I am familiar with engine oil formulations since the early
1970’s and have seen a lot of information on oil formulations back into
the 1950’s.
Although
Castrol is sold in more than 100 countries around the world, products and
the range of products are not the same in all countries. The oils sold in
Australia are not the same as the USA. There a range of reasons for that
including different market needs, mix of vehicles and climatic conditions.
The range and type of oils we sell in Australia are decided by people in
the Australian business not by people in the USA or Europe. The people
involved are a combination of Marketing, Sales and Technology. Our Sales
and Marketing people are just as keen to have the best products that suit
our market as we are in technology and you the customers’ desire for
your vehicles.
There
are two main industry oil qualification systems. These are API/I LSAC from
USA and ACEA from Europe. Both of these systems are developed jointly
between the oil industry and vehicle manufacturers. The updates reflect
the latest requirements for standard vehicles and applications. The
biggest influence most recently is the “Tier 2” emission regulations
in the USA and Euro 4 in Europe. These regulations do not come into place
for petrol engines in Australia until between July 2008 and July 2010.
The
US petrol classifications have two types, ILSAC grades for GF-3, GF-4 etc.
are; SAE 0w-30, 5w-30, 1 0w-30, 0w-20, 5w-20 and the rest, not ILSAC. The
ILSAC requirements require improved fuel efficiency and have chemical
limits on Phosphorus and Sulphur. API performance qualifications started
at SB in the 1930s, currently the highest API petrol engine specification
is SM. ACEA specifications are A1/B1, A3/B3, A3/B4 and A5/B5. ACEA C1, C2
and C3 are newer low Phosphorus specifications.
The
Phosphorus is limited to help maximise the life of catalytic converters
for long-term emission reduction. Sulphur mainly effects base oil type so
I will not discuss it further here.
The
main reason Phosphorus is added to engine oil is for cam and tappet wear
protection. The most widely used form of Phosphorus in engine oils is in
an organometallic molecule. The material is Zinc Dialkyl Dithio Phosphate,
ZDDP or ZDTP for short. Useful molecules that include Sulphur and
Phosphorus, they perform most of the antiwear protection on steel
surfaces. The most recent API SM/ILSAC GF-4 grades have reduced the
maximum allowable Phosphorus content to 0.08% (800 PPM, Parts per Million)
from 0.10%, 1000 PPM.
The
0.10% limit has been in place for approx. 15 years in the USA and since
1986 in Australia. Yes most petrol engine oils for more than 20 years in
Australia have been 0.10% Phosphorus maximum. That was as a result of an
agreement between the car industry and the oil industry in Australia. That
engine oils for petrol engines would be 0.10% Phosphorus maximum. 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.
The
majority of the Castrol passenger car lubricants sold in Australia are
ACEA qualified as well as API qualified. The ACEA requires extra valve
train wear, VTW, tests over and above API requirements. In addition most
of Castrol ACEA qualified products are 0.10% Phosphorus maximum. The same
as we have used for 20 years or more. So that is why some of our ACEA
qualified oils only claim API SL even though they pass all API SM engine
performance requirements, the Phosphorus content is above the maximum
level allowed for ILSAC grades.
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. Future generations
of these oils will also have Phosphorus limits and be lower over time for
the same reasons as for passenger car engine oils.
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.
In
Australia we have many people rebuilding older vehicles and engines. Many
of these people choose to put a modified cam into the engine when it is
rebuilt. That is often the case even though they do not plan to get
involved with Motorsport and the engine spends most of it life at low RPM.
Modified cams with higher lift often require stronger or dual valve
springs. All of these modifications increase load on the valve train and
increase the likelihood of wear on cams and tappets.
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.
Also
ZDDP is temperature activated so running the engine at low oil temperature
also accelerates cam and tappet wear. Some years ago a race team contacted
us after wearing out three camshafts during run-in on a dyno. They ran the
oil at approx. 50°C. We recommended take the oil to 85°C, no more cam
wear issues.
In
summary most of the Castrol passenger car engine oils sold in Australia
are still formulated to 0.10% Phosphorus maximum, the same as we have had
for the last 20 years but higher than was used in the 50’s and 60’s.
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
prelubed 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.
Castrol Edge Sport 25w-50, previously Formula R 25w-50 and before that
GP50, is specifically part of our performance range of engine oils for
push rod, flat tappet engines.
It
has demonstrated excellent wear protection on radical cam profiles.
Although rated API SG it incorporates the latest detergents and
dispersants for good engine cleanliness, contains 0.10% Phosphorus and
retains components for strong wear protection. The off-the-shelf product
is widely used in competition engines.
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.
