What is the difference between single & multigrade engine oils?
A single grade oil such as SAE 30 has certain temperature limitations. In very cold weather it will not flow. Even so there are many engines that need a single grade oil check your owner’s manual. Multigrade oil can be used across a wide range of temperatures because multigrade contains additives called viscosity improvers. SAE 15W/40 oil is a multigrade for example the “15W” indicates the oil viscosity at low temperatures the “W” meaning “winter”. The lower the number in the front of the “W” the greater the oils ability to flow at low temperatures. The “40” indicates the oil viscosity at normal engine operating temperatures. Most engines use multigrade oils.
