Have you ever stare blankly at a wall of motor oil in the store, wondering what all those numbers and letters mean? Numbers like 5W-30, 15W-40, 10W, – do you know what they mean? Do you care to know if it could cause any damage to your car/it’s engine if wrong specifications are used?
The numbers on motor oil can range from 0 to 60 and are determined in laboratory tests by the Society of Engineers (SAE).
These numbers refer to viscosity, or thickness, with the lowest numbers representing the thinnest, and therefore the most viscous oil. Also, the ‘W’ stands for ‘Winter,’ and refers to oil that maintain viscosity even in cold winter temperatures.
The need for different grades of oil is readily apparent when the weather switches because the temperature has a dramatic effect on the viscosity of the oil.
For instance, a 40-weight oil may be perfect for a long road trip in the summer when the engine is nice and hot but turn to sludge in the winter. On the other hand, 5 –weight oil may work best in the middle of winter when temperatures are in the single digits, but provide very little lubrication after the snow melts.
What do these numbers on motor oil mean?
Because of this, most motor oils on the market today are multi-viscosity oils, meaning they are formed from different grades of oil and share the characteristics of both thick and thin oil.
For example, a 5W – 30 oil will have the viscosity of a 5-weight oil when the engine heats up. If you’re not sure which grade of motor oil to use, consult your owner’s manual.
Most manufacturers recommend something around 10W-30 but there are circumstances that however, may call for different types of grades.