Machinery Lubrication magazine published by Noria Corporation
Issue link: https://www.e-digitaleditions.com/i/756816
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. 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 cata - lyst, 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. Typically, there are two catalysts in a cata- lytic converter. One tackles nitrogen- oxide pollution using a chemical reaction called reduction (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 cata - lyst 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 sulfur, can severely cripple the converter's ability to perform its job. Therein lies the first major difference between PCMO and heavy-duty diesel oil. Diesel engine oils have a higher anti-wear load in the form of zinc dial - kyldithiophosphate (ZDDP). Catalytic converters in diesel systems are designed to handle this additive, but gasoline systems are not. This is one of the main reasons you don't want to use diesel engine oil in your gasoline engine. Effects of Switching Engine Oils Viscosity is the single most important property of a lubricant. For engine oils, in ENGINE OILS C UNDERSTANDING 54 | November - December 2016 | www.machinerylubrication.com BACK PAGE BASICS mich A el BroW n | Nori a Corpor at ioN A u t o m o t i v e " " 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. the Differences