You'll see a wide selection of viscosities. Look in auto parts stores and you'll see oils labeled for all kinds of specific purposes: high-tech engines, new cars, higher-mileage vehicles, heavy-duty/off-road SUVs, and even cars from certain countries. Once the engine is running, the oil heats up, which is why a higher second number is especially important for extreme uses and hotter-running, more complicated engines. However, synthetic oils can be formulated to flow even more easily when cold, so they are able to pass tests that meet the 0W rating. A lower number is better before the W for cold-weather performance, so a 5W oil is typically what's recommended for winter use. If the oil is too thick, the engine requires more energy to turn the crankshaft, which is partly submerged in a bath of oil. Excessive thickness can make it more difficult to start the engine, which reduces fuel economy. Meanwhile, in low temperatures, oil has to be resistant to excessive thickening so it can still flow properly to all the moving parts in your engine. The more resistant oil is to thinning, the higher the second number (10W-40 versus 10W-30, for example) will be, and that's good. With the right additives to help it resist thinning too much in the heat, an oil can be rated for one viscosity when cold and another viscosity when hot. Within reason, thicker oil generally maintains a better film of lubrication between moving parts and seals vital components of your engine better. Motor oil becomes thinner and runnier as it heats up and thickens as it cools. Most motor oils’ viscosity is rated based on how thick it is at zero degrees Fahrenheit (represented by the number preceding the W, which stands winter, as well as its thickness at 212 degrees (represented by the second number after the dash in the viscosity designation). Viscosity refers to a fluid's resistance to flow. The starburst symbol on the left indicates that the oil has passed the service tests listed in the other doughnut. It also provides the SAE ( Society of Automotive Engineers) viscosity number and tells you if the oil has passed the Resource Conserving test. The API doughnut on the right tells you if the oil meets a current service rating. These are the labels you'll find on every container of reputable motor oil. Those are the basics, but there's a whole lot more to the story than that. As of this writing, that includes SP, SN, SM, SL and SJ for gasoline engines and CK-4, CJ-4, CI-4, CH-4 and FA-4 for diesels.
OIL VISCOSITY CHART FULL
API has a full list of these standards here in case you’re curious, but make sure you’re buying an oil that’s been tested under a current standard. These letters are based on a group of laboratory and engine tests that determine the oil’s ability to protect the engine from wear and high-temperature deposits and sludge. API's latest service standards are SP for gasoline engines and CK-4 for diesels. You’ll also notice a two-character service designation on the container. Always choose an oil from a brand that displays the starburst symbol that indicates the oil has been tested by the American Petroleum Institute (API).
OIL VISCOSITY CHART MANUAL
For regular use in moderate temperatures, what’s listed in your owner’s manual is fine. You should adjust which weight and type for the seasons and your expected use of the car, which we’ll explain below. That number refers to the viscosity (or thickness) of the oil that you should use. The owner's manual for your car will list its recommended oil weight, whether that's a standard format like 10W-30 or something more unusual.
While there is a mountain of information about the various oil choices, the first step is honestly quite simple: Look in your car’s manual. Given all the options for motor oil options out there, choosing the right oil for your car might seem like a daunting task.