Oil grades
As defined by the Society of Automotive Engineers (SAE), the first part of the viscosity designation (W grade, as in ''Winter'') is an indication of the product's ability to help an engine crank and start, and for the engine to pump the lubricant. The lower the number (0W is the lowest, 60W is the highest), the lower the temperature the product can be used at. The second part is related to the viscosity, or thickness, your engine oil sees at operating temperature.
Essentially, if you read ''5W30'' on the label, it means the oil will behave similarly to an SAE 5 oil at cold temperatures but like an SAE 30 oil at normal engine temperatures. Note that the numbers refer to Fahrenheit units.
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Most cars, trucks and SUVs require 5W30 or 5W20 oil. If you plan to change the oil yourself, make sure you follow the automaker's recommendation before purchasing a bottle.
Oil types
With all that in mind, you can determine the type of oil that you want. If you take your car to the shop, a technician will ask you to make a choice. Here are the possibilities:
Conventional
As the least expensive of the three types, conventional oil is basically a byproduct of the crude oil refining process. Less complex in design, it's prone to quicker deterioration, especially when exposed to high levels of heat, and gives off more sulphur as well as other pollutants.
Synthetic
Developed from chemical compounds, synthetic oil is much cleaner than conventional oil. It's also more stable in most temperatures and under most demands while offering reduced viscosity and wear. Moreover, truck owners use it to increase payload capacity. Synthetic oil is more complex to make and therefore more expensive to buy.
Synthetic blend
A synthetic blend combines some of the properties of the two other types of engine oil. It's essentially a conventional motor oil with high-performance elements, added to help it burn more cleanly and withstand greater temperatures. Manufacturers are able to offer some of the benefits of synthetic oil, while keeping the cost closer to the price range of conventional oil.