Here - read some of this. Yes, the ZDDP has been removed from most major brand oils but it still used in many off-road HD oils. The new "triple protection" Shell Rotella removed much of the ZDDP to confrom with 2007 and newer emissions requirements.
Zinc Dialkyl Dithiophosphates
widely used as an anti-wear agent in motor oils to protect heavily loaded parts, particularly the
valve train mechanisms (such as the camshaft and cam followers) from excessive wear. It is also
used as an anti-wear agent in hydraulic fluids and certain other products. ZDDP is also an
effective oxidation inhibitor. Oils containing ZDDP should not be used in engines that employ
silver alloy bearings. All car manufacturers now recommend the use of dialkyl ZDDP in motor
oils for passenger car service.
Many camshaft manufacturers recommend the use of diesel oils, many even name old forumla Shell Rotella
T (CI-4 formulation) as their preferred engine oil, along with some form of Zn and P additive,
such as GM EOS. The only mention I have seen as to a reason not to use a diesel oil would be
the lack of friction modifiers in diesel oils vs car oils or the fact that they may contain more of the
Aryl ZDP rather than the Alkyl ZDP, but on the other side of the fence, usually friction modifiers
are typically only used in very low viscosity motor oils that don't have the levels of Zn and P we
are looking for.
Although difficult to find, some manufacturers are continuing to produce their CI-4 oils, some of
which can be found at your local auto parts stores. Check the label. If it says CI-4 or CI-4+
alone with no mention of a CJ-4, it's probably has the needed antiwear additives needed for
most older engines, gas and diesel.
Zinc Dialkyl Dithiophosphates
widely used as an anti-wear agent in motor oils to protect heavily loaded parts, particularly the
valve train mechanisms (such as the camshaft and cam followers) from excessive wear. It is also
used as an anti-wear agent in hydraulic fluids and certain other products. ZDDP is also an
effective oxidation inhibitor. Oils containing ZDDP should not be used in engines that employ
silver alloy bearings. All car manufacturers before 2007 recommend the use of dialkyl ZDDP in
motor
oils for passenger car service.
ZDDP was the most commonly used additive in engine oil for sixty years and is a
multi-functional additive which provides the wear protection in almost all engine oil formulations.
In very simple terms, ZDDP, when heated in the high temperatures of the engine, decomposes
to form an extremely thin layer of phosphorous glass over the engine surfaces (sometimes
referred to as "glassivation"). This new layer of glass is perpetually worn away and replenished,
protecting the metal surfaces from wearing away.
The problem for 2007 is that while ZDDP works to protect engines very nicely, it has other
performance features that have become "possibly" detrimental in modern automotive engines to
certain parts of the emissions and exhaust systems.
Oil companies have been cutting back on the use of Zn and P as anti-wear additives, and
turning to alternative zinc-free (ZF) additives and ash-less dispersants since Zn, P, and sulfated
ash have been found to be bad for catalytic converters (new low SAPS oils).
This reduction is a mandate issued by API, American Petroleum Institute, who is in charge of
developing standing standards for motor oils. The latest API SM standard for car oils calls for a
zinc and phosphorus content less than 0.08% to reduce sulfur, carbon monoxide, and
hydrocarbon emissions. As a result of this mandate, some motor oils now have as little as
0.05% zinc and phosphorus - including Shell Rotella T "Triple Protection" blend. Prior to the
new CJ-4 API standard for diesel oils, we found most
of the CI-4 15w40 and 5w40 oils to have excellent levels of Zn and P.
These new API guidelines do not need apply to “racing,” “severe duty,” or any motor oils that
do not carry an API “starburst” seal or clearly state for off-road-use only. Motor oils meeting
“Energy Conserving I or II” standards should be avoided as well as those with an API SM
classification, with it's lower Zn and P levels, which applies only to 0w20, 0w30, 5w20, 5w30,
and 10w30 "ILSAC" GF-4 grades. Although having been more sensitive to emissions and the
environment than American standards, we find the European ACEA A3 and B3/B4
classifications, which place a cap on P levels at 0.10-0.12%, to be better in taking into
consideration wear and engine longevity while limiting emissions and protecting emissions
control devices.
Although difficult to find, some manufacturers are continuing to produce their CI-4 oils, some of
which can be found at your local auto parts stores. Check the label. If it says CI-4 or CI-4+
alone with no mention of a CJ-4, it's probably good.
From Mobil:
The active ingredient that you are talking about is phosphorus which is added thru a component
called ZDDP. For products that meet the new ILSAC GF-4 specification the phosphorus levels
for the oil must be less than 800 ppm phosphorus. The ILSAC level for phosphorus has been
reduced to protect the catalytic converter and other emission protection equipment. The engine
manufacturers are confident that this level of phosphorus will protect both new and older
engines. However, there are Mobil 1 products which have a higher level of phosphorus (phos)
and can be used in engines in racing or high performance applications; see the attached
Mobil 1 Turbo-Diesel Truck - has 1100 PPMs of Zinc via ZDDP. Most diesel applications.
Applications requiring higher phosphorus (ZDDP), including engines with diesel particulate filters.
CJ-4, CI-4, CI-4 Plus, SM, SL
