Continuously measure the speed and running time of your engine to monitor its performance and detect mechanical issues early. These meters can be programmed based on engine run time to light up for maintenance reminders, such as oil changes, filter replacements, and inspections. Wrap the signal wire four to five times around your spark plug to secure it in place. They’re battery powered, so they will start showing readings as soon as you turn on the engine. It adjusts to nine different engine types for accurate readings.