MACHINERY LUBRICATION- INDIA SEPTEMBER-OCTOBER 2019 | Page 15

Michael Brown | Noria Corporation
AUTOMOTIVE
UNDERSTANDING
the Differences
in ENGINE OILS
C
Additive Packages and
Catalytic Converters
A catalytic converter is the large metal
box bolted to the underside of your car.
It has two pipes coming out of it, with
one for the “input” and the other for the
“output.” The converter’s input pipe is
connected to the engine and brings in
hot, polluted fumes from the engine’s
cylinder head. The output pipe is
“
attached to the tailpipe. As gases from
the engine fumes move over the catalyst,
chemical reactions occur, breaking
apart (cracking) the pollutant gases
and converting them into other gases
that are safe enough to blow harmlessly
into the air.
“
ontrary to popular belief,
there are major differences
between passenger car
motor oil (PCMO) and
heavy-duty diesel oil. The main
distinction is in the additive packages.
PCMO has lower detergent and anti-
wear (AW) additive levels. The AW
additive alone can play havoc with
components like catalytic converters.
This is why you do not want to mix up
these engine oils or use one in place of
the other.
Typically, there are two catalysts in a
catalytic converter. One tackles
nitrogen-​
oxide pollution using a
chemical reaction called reduction
For engine oils, the selected viscosity must
allow the oil to be pumpable at the lowest
startup temperature the vehicle will experience
while still protecting components at in-service
temperatures.
(removing oxygen). This breaks up
nitrogen oxides into nitrogen and
oxygen gases, which are essentially
harmless because they already exist
naturally in the air. The other catalyst
works by an opposite chemical process
called oxidation (adding oxygen) and
turns carbon monoxide into carbon
dioxide. Another oxidation reaction
converts unburned hydrocarbons in the
exhaust into carbon dioxide and water.
In effect, three different chemical
reactions are occurring at the same
time. After the catalyst has done its job,
what emerges from the exhaust is
mostly nitrogen, oxygen, carbon dioxide
and water (in the form of steam).
Some of the byproducts of combustion,
including lead, zinc, phosphorus and
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