Servicing tool
Generator service due checker
Enter the hour meter reading, the hours and date of the last service, and the interval from the manufacturer’s schedule. The checker tells you whether the next service is not yet due, approaching, overdue, or whether there is not enough information to say.
Intervals vary by engine, so the checker uses the one from your own schedule. The service intervals guide lists typical published intervals and explains how hour and calendar limits work.
Free to use · No login · Works on a phone
How the check works
- Hours since the service = current hours − hours at the last service.
- Months since the service are counted from the last service date to today.
- A service is due at the hour limit or the calendar limit, whichever comes first.
- Approaching means within the last 10% of either interval. Overdue means either limit has been reached.
- If neither limit can be checked, the result is “insufficient information” rather than a guess.
Where to find the figures
- Current hours: the hour meter or the controller display.
- Hours and date of the last service: the service sticker, logbook or invoice.
- The interval: the maintenance schedule in the manual for that engine or generator. The data plate identifies the model.
Published examples, not your schedule
These are published examples for particular products. They show how schedules are written. They are not the interval for your generator, and the checker never fills them in for you.
- Generac home standby generators: oil and filter every 200 hours or 2 years, whichever comes first (100 hours in very hot or cold conditions). Source: Generac support: maintenance schedule for home standby generators
- Honda portable generators (as reported): first oil change at 1 month or 20 hours, then every 6 months or 100 hours. Source: SlashGear: How often you need to change the oil in your generator
- Diesel generators in continuous emergency operation (US FEMA course material): oil and filter every 240 operating hours. Source: FEMA IS-815: Operational generator servicing requirements
Worked example
A diesel standby set reads 1,430 hours. It was last serviced at 1,250 hours on 14 March 2026, and its manual gives 250 hours or 12 months. On 14 October 2026 that is 180 hours and 7 months since the service: 72% and 58% of the limits. Status: not yet due, with 70 hours or 5 months left, whichever comes first.
What the result does not tell you
- It never shows that a generator is safe to run or in good condition.
- Standby sets that rarely run still age: batteries, coolant, fuel and rubber parts deteriorate with time. That is why calendar limits exist.
- Dust, heat, many short runs or long continuous runs can justify servicing sooner. The manual may have a severe-duty schedule.
- Faults between services are not covered by any interval. If something seems wrong, use the symptom finder or call.
Book a generator service
ProService Generator Repairs works onsite across Gauteng. Send the generator details on WhatsApp or call to arrange a visit.