Short answer
Preventive maintenance is planned servicing of a diesel generator on a calendar or by running hours, so faults are found on a scheduled visit and not during a power cut. A typical visit covers oil and filters, the cooling system, batteries and the control panel, and ends with a written service report.
What a visit typically covers
An initial health assessment of the generator Oil and filter replacement as per the agreement Cooling system inspection Battery checks Control panel inspection A service report and a maintenance history for the set
Calendar-based or running-hour-based
Some generators are serviced on fixed dates. Others are serviced by running hours, which suits sets that run often. Standby sets that rarely run are usually kept on a calendar so they are still checked even when the hour meter hardly moves. The right basis for your set depends on how it is used.
Why records matter
A maintenance history shows what was done and when, so the next visit starts from facts, repeat problems stand out, and a buyer or auditor can see the set has been looked after.
Follow the maker’s manual
Service intervals and the exact work differ between engine makes and models. We follow the schedule in the applicable manual for your engine, and agree the scope with you before we start.
Written by the S. Y Diesel Services team. Published 2026-11-10. General guidance only: the engine maker’s manual and a site inspection decide the exact work for your generator.