Hey, where's all the Zinc?
An Oil Dilemma
O.K. it seems as if a hornet's
nest is about to be provoked. Grab a stick, we'll all poke at it.
A lot of controversy concerning the government's recent mandatory reduction of
phosphorous and zinc content in motor oils has been surfacing lately. Newer vehicles
engines are designed with tight tolerances, therefore lighter weight oil is generally
specified. They also run at higher temperatures to reduce exhaust emissions.
Thermal breakdown and dilution are the biggest enemies of the lubricants ability
to achieve its optimum performance.
Zinc and phosphorus compounds work hand in hand to build a protective barrier
against metal to metal contact when under extreme pressure with the added benefit
of corrosion protection.
Owners of older cars that have larger bearing surfaces and looser tolerances
feel like they are getting the shortest of the poking sticks.
Numerous additives have been developed and incorporated in engine oils though
the years. A staggering array of formulas can be found in any parts supply house.
Why does everything have to become so complicated in this, the era of the synthetic
Multigrade oils contain polymers that effect the oils viscosity reaction through
a broader temperature range. These polymers link together chains of molecules to
keep viscosity more consistent. The problem with these multigrades is their working
life is shortened as the polymers break down, leaving the zinc compound that remains
as the last line of defense against friction and corrosion.
Because newer cars use oxygen sensors and catalytic converters, high milage vehicles
often suffer from zinc deposits accumulating on these components.
Since the governments zinc reduction targets the lighter multi-grade oils (10w-30
and thinner), single or heavy multigrades are not as adversely effected and usually
contain a higher percentage of zinc comparatively. Perhaps a combination of two different
grades would give improved protection. ie 20w/50 + 5w/30 .
The old muscle car era vehicles engines use high pressure valve springs and flat
faced tappets or lifters. Extra protection is critical during the break-in process
(after a rebuild is performed) to prevent scuffing wear or galling and premature
failure of the parkerized surfaces of the camshaft, which in turn ruins the lifters.
Not all camshaft and lifters use the highest quality materials. Beware of cheaply
made imported items of inferior steel, particularly lifters!
Anytime cam and lifters are replaced, a special camshaft/lifter break-in lubricant
that contains concentrated amounts of molybdenum and zinc must be applied to protect
against metal to metal contact. Many experts claim that adding this moly lube when
changing oil can extend the engines life.
Molybdenum is a compound element that has been proven to provide exceptional
resistance to friction and corrosion. It is a more costly additive than zinc/phosphorus,
but some of the better oils include it in their formula.
Proper engine break-in procedures must be followed to prevent initial cam wear.
New engines first start should be allowed to run from 1700 to 2000 R.P.M. for about
twenty minutes or more. This keeps the lifters from imposing extreme pressure on
the toe of the cam lobe. Pre-oiling the engine by spinning the oil pump manually
is also a wise idea, to help reduce effects from a ''dry start''. This method also
tends to flush away any contaminates that may be lurking in the oil galleys and passage
Synthetic oils are usually not used for break-in oil as it interferes with the
piston ring's ability to seat in. 30 weight or lighter non-detergent conventional
oil is customary for the first 1000 miles or so. Much controversy on this issue exists.
Careful consideration must be given if an over the counter oil additive is used,
as it may not be compatible with your own oils delicate concoction of additives!!
Adding extra zinc to an older cars engine can increase protection against wear. On
newer cars, O2 sensor and catalytic converter damage could result.
Oil formulated for diesel engines tend to have higher levels of zinc-phosphate,
but are not designed for gasoline's dilution contaminates.
In the early years, synthetic oil was developed and used in Europe, as petroleum
products were expensive. Lack of refineries made petroleum availability poor. The
first synthetic oils were not compatible with petroleum based oils and when mixed,
turned into a jelly-like goo.
The best advice I can offer is use a quality oil and change it often. Single
grade oils usually don't incorporate the polymers designed to extend their operating
temperature range, but early cars generally recommended single weight oil anyway.
The eeney meeny miney mo system of choosing your lubricants could lead to the
early demise of your vehicles power plant. Choose well my friend.
Read your owners manual for oil recommendations.