As the pressure to reduce fleet costs while increasing vehicle uptime has magnified, maintenance managers are trying to get every mile possible out of an oil change. Maintaining engine lubricating oil is a very important element in stretching the productive life of vehicle engines. Often referred as the life blood of the engine, the oil circulates through the engine, performing critical functions necessary to maintain engine performance and maximize useful service life.
“First and foremost, engine oil provides lubrication which keeps moving parts apart; reduces friction; transfers heat; protects against wear; and prevents or minimizes corrosion deposits, debris and contaminants,” explains Jim McGeehan, global manager, diesel engine oil technology, Chevron Global Lubricants. “Other roles played by engine oils include dispersing soot to minimize its effect on viscosity increase; improving low temperature cranking and pumpability for cold starts; and minimizing oil consumption and its effect on exhaust aftertreatment systems.”
Engine oil has four main functions, elaborates Mark Betner, product manager, heavy duty lubricants, Citgo Petroleum Corporation:
Prevent or minimize friction and wear that is caused by corrosion, metal contact and contaminants. Valve train and bearings are critical areas of engine needing optimum wear protection.
Control deposits or keep the engine clean as possible, especially in critical areas of engine such as upper piston surfaces and valve deck. Failure to control upper piston deposits can lead to an increase in oil consumption and ring/piston damage and eventual engine failure.
Control soot from combustion byproducts which can lead to oil thickening, premature filter clogging and engine wear. The oil has a dispersant additive system that performs this function and newer CJ-4 oil technology is the best ever at performing this function.
Have the appropriate viscosity to influence both low and high temperature protection and fuel economy.
“All API CJ-4 motor oils provide a significant improvement in wear protection, soot and deposit control and high-temperature oxidation stability over API CI-4 Plus motor oils,” notes Dan Arcy, OEM technical manager, Shell Lubricants. “API CJ-4 motor oils were designed to meet the needs of the 2007 emission engines, as well as provide improved protection for engines built prior to 2007. In addition, CJ-4 performance is the recommended performance for the new 2010 emission engines.”
Engine oil needs to be changed on a regular basis because oils can lose their performance properties over time as a result of heat, contamination and chemical deterioration. Engine oils oxidize and become loaded with soot, wear debris and contaminants which can only be removed by draining the oil, Chevron’s McGeehan explains. Oxidative products and acids formed as a byproduct of combustion also degrade the oil, adds Shell’s Arcy.
Additives built into the oil to help protect critical engine parts become depleted from neutralizing acids, controlling oxidation and nitration and providing sacrificial films to minimize wear. As the additives are depleted by decomposition, their functionality is decreased, McGeehan says. “All of which will have a negative effect on the performance of the engine oil, contributing to acid formation and increased wear, which can lead to corrosion, among other things.”
Oil drain interval recommendations are determined through extensive testing by OE engine manufacturers. These guidelines include fuel consumption, oil consumption, fuel quality (ultra low sulfur diesel, percent biodiesel, etc.), sump capacity, filtration system (filter type and capacity), oil quality, ambient temperature and maintenance practices, points out Chevron’s McGeehan.