Preventive maintenance (PM) is service performed on a fixed schedule, by calendar time or by usage, to reduce the chance of a breakdown. Filter changes, inspections, cleanings and tune-ups are all preventive maintenance.
PM is the opposite of reactive work. Reactive work starts with a failure. PM starts with a date.
How to measure preventive maintenance
The main measure is whether the planned visits actually happen on time:
PM compliance = PM visits completed within their window ÷ PM visits due in the period
Say 120 PM visits were due in March and 102 were completed within their allowed window. PM compliance is 102 ÷ 120, or 85%.
A second useful measure is the share of your work that is planned:
Planned work share = PM hours ÷ Total field hours
Track it monthly. It tells you how much of your schedule you can set in advance and how much arrives as surprises.
Why it matters
PM is the most schedulable work you have. You know the customer, the site, the equipment and roughly how long it takes, weeks ahead. That makes it ideal for filling the board in a way that keeps travel low: group visits by area, put them next to reactive jobs nearby, and move them into quieter weeks.
The catch is that PM is also the first thing to slip when the board fills with urgent calls. Visits get pushed, then pushed again, and compliance falls without anyone deciding it should. The preventive maintenance scheduling guide covers building PM into the calendar so it survives busy weeks, and maintenance agreement scheduling covers the contract side.
When you place PM visits, put them where the truck already is. A PM booked next to other work in the same service territory adds a short drive. The same visit booked alone at the edge of the map adds a long one.
A common mistake
Scheduling all PM visits in a fixed sequence, such as by contract start date, instead of by location. The visits are flexible within their window. Using that flexibility to cluster them by area is where most of the savings come from.
Related terms
- Predictive maintenance uses equipment condition, not a calendar, to decide when to service.
- Recurring service is the scheduling pattern PM usually follows.
- Mean time between failures is one way to judge whether PM is working.
Common questions
How often should preventive maintenance be done?
Follow the equipment manufacturer's recommendation as a starting point, then adjust based on the site's conditions and service history. Equipment in harsh environments often needs shorter intervals.
Is preventive maintenance worth it for small companies?
It usually brings steady, schedulable work and recurring customers. Whether it pays depends on what you charge for it and how efficiently you route the visits.
What is the difference between preventive and corrective maintenance?
Preventive maintenance happens before a failure, on a plan. Corrective maintenance fixes something that has already failed or been found faulty.