Final answer:
To ensure proper function and avoid mechanical issues, check your truck's air compressor's oil level before first starting the engine, when it's new, or upon installation. Subsequently, perform daily checks or follow the manufacturer's service interval recommendations.
Step-by-step explanation:
If your truck's air compressor has its own oil supply, it is essential to check the oil level regularly to ensure the compressor functions properly. The first time you should check the oil level would be before you first start the engine, when the truck is new, or when the air compressor is newly installed. After that, it should be checked daily or according to the manufacturer's recommendations, which may suggest checking at regular service intervals since the sight glass only shows if there is enough oil to cover the sight glass.
Ensuring an adequate oil level is crucial because the oil lubricates the moving parts within the compressor, reducing friction and preventing overheating or damage. Driving a truck with an air compressor that has low oil levels could lead to serious mechanical issues, potentially causing a breakdown or even an accident.