Feature
14-22 TechFeat Oil 2/17/14 3:17 PM Page 14
Choosing the ‘Right’ Oil Motor Oil Can Make or Break an Engine BY LARRY CARLEY, TECHNICAL EDITOR
E
very engine builder knows the importance of using not only high-quality motor oil in an engine, but also an oil that has the right additive package and viscosity for the application. This is especially important in performance applications where extremes of heat and pressure can push many ordinary motor oils to the brink. Motor oil can make or break an engine. It lubricates the main and rod bearings, cylinders, pistons and rings, the camshaft and valve train. It helps cool the bearings, pistons and valve springs, and in turbochargers it keeps the shaft bearings alive. Oil also helps disperse and neutralize combustion byproducts and moisture that end up in the crankcase, and it helps keep the engine clean. The additives that are used in motor oils can vary quite a bit as can the base stocks that are used to formulate any given motor oil. Additives make up about 20 to 25% of a quart of oil. Additives help boost the performance level of the base stock oil, and include Viscosity Index Improvers that allow multi-viscosity oil to flow more easily at cold temperatures while retaining film strength and viscosity at high temperatures. The blend of base stocks and additives is what distinguishes one motor oil from another. So don’t think all motor oils are more or less the same. Even motor oils that have the same viscosity rating and service ratings may perform quite differently depending on the situation. 14 February 2014 | EngineBuilder
Types of Oil When it comes to choosing a motor oil for a given engine application, you have a lot of options from which to choose. There are conventional motor oils made from refined petroleum, various types of “synthetic” oils, “synthetic-blends” and “semi-synthetics.” Synthetic oils are typically made up of extremely refined or “hydro-isomerized” oils, called Group III oils by the API (American Petroleum Institute). For extremely demanding applications blends of “PAO” (Polyalphaolefin) and “POE” (polyol ester) base oils are used, which are API Groups IV and V, respectively. Synthetics provide the best lubrication at both ends of the temperature spectrum, flowing more easily at cold temperatures while resisting
The additives that are used in motor oils can vary quite a bit as can the base stocks that are used to formulate any given motor oil.
viscosity breakdown, oil consumption, oxidation and sludging at high temperatures. Synthetic-blends and semisynthetics are a more affordable alternative to a full synthetic, and typically contain less than 30% synthetic oil by volume. Blends help bolster the performance properties of conventional oil, and are a step up from an ordinary Group II base oil. In fact, most of today’s “conventional” 5W-20 and 5W-30 multi-viscosity oils are actually blends and contain a certain amount of Group III oil. As for the various additives in oil, many are necessary to achieve the minimum API requirements for multi-viscosity rating, wear resistance, cleanliness and so on. API rates motor oils differently if they are