Differences between 15W40 and 10W30. Viscosity: The main significant difference between 15W40 and 10W30 is viscosity. Viscosity is the oil’s resistance to flow at a specific temperature. The first two number in the oil SAE grade (15w or 10w) refers to the oil’s viscosity at cold temperatures. Lower the number, and easily flow in cold engine
Thin, low viscosity oils flow easier to protect engine parts at cold temperatures. The faster oil flows to critical parts of the engine, the more protected they are from wear. So a 5W-30 will flow easier than a 10W-30 at start-up temperatures. And a 10W-30 will flow easier than a 15W-40 at normal engine operating temperatures.
On the other hand, you may use a 5W viscosity grade where a 10W or 15W is recommended to provide faster lubrication to engine components during start-up. However, there are some drawbacks to consider. For instance, since a lighter base stock is used in the 5W formula, the lubricant may have more evaporation than a 10W or 15W.
The main difference between 10W-40 oil and 15W-40 oil is that 15W-40 oil has a higher viscosity than 10W-40 oil. 10W-40 oil allows the engine to run freely.
The 10W 40 oil is thicker and is thought by many to be more efficient. 15w40 is thicker at all temps vs 10w30.
What is the difference between Formula 4-Stroke® 10W-40 Synthetic Scooter Oil and 10W-40 Synthetic Motorcycle Oil? Answer: AMSOIL 10W-40 Synthetic Motorcycle Oil contains a robust additive package designed for the extreme pressures and high temperatures common in motorcycle applications.
