Motor oil helps lubricate an engine to reduce friction and maintain smooth movement of working parts, thereby increasing performance. There are three main types of motor oil: conventional, synthetic, and synthetic blend, the last of which combines some of the properties of the first two. Within these types, there are different grades or weights that are used for specific purposes.
Most equipment such as cars, boats and even mowers, offer suggestions in the owner's manual regarding which weight is appropriate for the engine. Single grade is the SAE distinction found on a bottle of oil, such as SAE40. This is a measurement of the oil's thickness and ability to withstand high temperatures. There is also multi-grade, for example, 10W40. This simply stands for the ability of the oil to withstand both hot and cold temperatures.
Conventional motor oil is the least expensive of the three types. It is basically a byproduct of the crude oil refining process. Because it is less complex in make-up, it is prone to quicker deterioration, especially when exposed to high levels of heat. Conventional motor oil also gives off more sulfur as well as other pollutants.
Synthetic motor oil costs quite a bit more than conventional oil or conventional/synthetic blends. This is because synthetic oil costs more to make. It is developed from chemical compounds called polyalphaolefins, abbreviated PAO. Its entire structure is different, making synthetic oil far cleaner and more stable than conventional motor oil. It is able to maintain proper viscosity, or flow, in most temperatures and under most demands.
Synthetic blends combine some of the properties of both of the other types of motor oil. Manufacturers are able to offer some of the benefits of synthetic oil while keeping the cost closer to the price range of conventional oil. Synthetic blends are not derived from the same substances as full synthetics. A synthetic blend is essentially a conventional oil with high performance elements added to help it burn cleaner and withstand greater temperatures.