What is the consequence of using oil with too low of a viscosity in a 4-stroke engine?

Using oil with too low of a viscosity in a 4-stroke engine leads to insufficient lubrication. Viscosity refers to the thickness or flow characteristics of the oil; if the oil is too thin, it may not provide an adequate film to protect engine components. This can result in increased wear and tear on moving parts, leading to potential engine damage due to friction and heat. Proper lubrication is essential for maintaining engine performance and longevity, as it ensures that components are well protected against metal-to-metal contact.

In contrast, while improper cooling could be a secondary issue if components are overheating due to insufficient lubrication, it is not the primary direct consequence of low viscosity oil. Increased fuel efficiency and extended oil life are generally associated with oils of appropriate viscosity and quality, not those that are too thin, which may degrade faster and actually cause poorer efficiency. Therefore, the primary concern with low viscosity oil is indeed the challenge it poses to effective lubrication.