What is one of the effects of inadequate lubrication in heavy equipment?

Inadequate lubrication in heavy equipment leads to increased friction between moving parts, which can cause overheating and significant wear and tear on components. As a result, the functional capacity of the equipment diminishes, meaning it may not perform tasks as effectively or reliably. This degradation can lead to breakdowns, necessitating repairs or replacements, and reduces overall efficiency during operation.

In contrast, the other choices are not associated with inadequate lubrication. Increased fuel efficiency, extended equipment lifespan, and enhancement of operational speed would generally relate to well-maintained equipment with proper lubrication. Therefore, the most accurate outcome of insufficient lubrication is indeed a decreased functional capacity.