Motor vehicle manufacturers set performance characteristics and standards for engine oil that petroleum companies are expected to meet. As of 2011, engine oil ratings for gasoline engines have changed 10 times since 1930, and engine oil ratings for diesel engines have changed 11 times since 1959. Conventional engine oils and synthetic engine oils, must meet the same specifications and ratings required by motor vehicle manufacturers.
Current oil service categories for gasoline engines are SM, SL and SJ. The SJ rating is for 2001 and older engines, SL is for 2004 and older engines and SM is specifically designed for vehicles manufactured since 2004 but will work for all gasoline engines. Whether you chose to use conventional or synthetic motor oil, the oil must meet these specifications. This principle applies to oil specifically manufactured for diesel engines. Diesel engine owners must ensure the oil they are using meets the manufacture's recommendation for their vehicle.
Conventional motor oils are petroleum based and are used more than any other type of oil. Motor oil is a byproduct of the crude oil refining process. Several naturally occurring elements that are hazardous to your engine are removed during refining, and other important chemicals that are beneficial are included before the product is bottled and shipped out for sale. Petroleum oil is degraded through oxidation, contamination and the engine's heating and cooling cycle.This is why it is essential to change oil according to manufacturer recommendations.
Many chemicals are added to petroleum-based engine oil to improve its ability to protect your engine. Oil companies add agents that aid in keeping oil flowing at cold temperatures, while helping engine starting and oil flow through the lubrication system. Viscosity agents help maintain the performance characteristic of oil under all operating conditions. Detergents are added to reduce and delay the buildup of deposits on internal engine parts, and corrosion inhibitors are added to prevent damage due to metal surfaces.
Synthetic oils are manufactured from organic esters and synthesized hydrocarbons. Synthetic oil manufacturers advertise that synthetic oil provides superior flow characteristics at low temperature, superior resistance to breakdown when exposed to high temperatures and keep helps engines cleaner. For these reasons, proponents of synthetic oil encourage longer intervals between oil changes. Regardless of synthetic oil manufacturer claims of longer oil change intervals, you must follow the oil change intervals required by your car's manufacturer to maintain your automobile warranty.
