Despite his engineering qualifications, McCoy was unable to secure a position as an engineer. He began working as a fireman on the Michigan Central Railroad. This job involved shoveling coal into the engine's firebox and oiling the engine parts. It was this experience that revealed the need for automated lubrication.

While working on the railroad, McCoy observed the inefficiency and downtime caused by manual lubrication. He began to develop designs for an automatic lubricator that would oil machinery while it was running, reducing wear and tear and increasing efficiency. The work was conducted on his own time, experimenting and refining his designs.

McCoy received his first patent, U.S. Patent No. 129,843, for an 'Improvement in Lubricators for Steam-Engines.' This patent marked a significant step in his career and established the foundation for his later inventions.

McCoy continued to work on improving his lubrication systems, obtaining numerous patents for different variations and applications. His inventions were widely adopted by railroads, steamships, and factories, contributing to increased efficiency and productivity.

In his later career, McCoy likely worked as a consultant or advisor to companies using his lubrication systems. He also sold the rights to some of his inventions, possibly to secure financial stability.