For engine oils, viscosity determines the speed it flows to protect the engine. The “W” stands for “winter,” the number infront of it indicates the oil’s viscosity (or thickness) at low temperatures (hence the W), and the number after it indicates viscosity at higher temperatures, when the engine is running. A greater number represents a higher viscosity, which means the oil is more viscous and more resistant to flow.

The key to selecting the correct lubricants for your vehicle begins and ends with the owner’s manual. It is critical to follow owner’s manual instructions, especially while the vehicle is still under warranty. Failing to follow the recommendations can void the warranty.

All engine oils are made of base oils and additives. Fully synthetic engine oils contain 100% non-conventional, high-performance fluids. Semi-synthetic engine oils (also called "blends") contain a smaller percentage of these high-performance fluids in combination with conventional mineral oil.

Semi-synthetic oil can achieve higher levels of performance than from mineral oil alone. Semi-synthetic oil is more wallet-friendly than fully synthetic oil as it comes at a reduced cost whilst still giving you some of the benefits of full synthetic oil.

Is synthetic oil better for my engine than conventional oil? Yes, synthetic oil is better for your engine than conventional oil. Although conventional oil (i.e., mineral oil) can provide adequate lubrication performance, it can't compete with the overall engine performance and protection provided by synthetics.

A short answer to this question is yes. Motor oil can only last for a certain period of time. For this reason, oil goes bad with time just by sitting in the engine. Over time, it becomes less viscous thus less efficient in maintaining proper lubrication between moving components. 

When you skip an oil change or go too long without one, the oil in your vehicle is unable to properly move through your engine. Skipping an oil change leads to the vehicle's oil thinning over time and catching a buildup of metal, dirt, and other particles.