Put plainly, preventive maintenance is servicing something on a schedule whether or not anything is wrong with it, and predictive maintenance is watching the equipment for signs that something is starting to go wrong and acting when it does. That is the whole difference. Everything else written about the two is a consequence of that one distinction, and this page walks through the consequences that actually matter to somebody deciding what to do about their own equipment.
The everyday comparison that actually holds
Preventive is changing the oil in a car every so many miles regardless of how the oil looks. Predictive is a warning light that comes on when something is genuinely wrong. Most people run their car on both without thinking about it, which is also how most sites run their equipment, and it is a better mental model than treating the two as rival philosophies.
Why preventive is what nearly everyone does
It needs nothing except a list of equipment and a decision about how often. No sensors, no baseline, no specialist. That means it can be applied to every item you own starting this week, and it is why it is the base layer at essentially every site, including the sophisticated ones with monitoring on their largest machines.
What predictive needs before it can tell you anything
Something measuring the equipment, a period of measurement to learn what normal looks like, and somebody who can tell a real change from ordinary variation. Those are real requirements, they cost money per machine, and they are why monitoring goes on a small number of important machines rather than on everything a site owns. The other thing worth knowing is that the two are not exclusive on the same machine. A monitored machine usually keeps a long interval as a backstop, so that if the monitoring itself quietly stops working, which it does, the machine is not left with no maintenance at all and nothing to say so.
Questions people ask about what is the difference between preventive and predictive maintenance
Which one should a small site start with?
Preventive, on the equipment whose failure would actually hurt. It works immediately, costs nothing to set up, and produces the history that would tell you later whether anything is worth monitoring.
Is one of them better?
Neither. They suit different equipment, and nearly every site ends up running both: intervals on everything, monitoring on a few important machines.
What is reactive maintenance?
Fixing something after it breaks. It is the third option, it is a legitimate deliberate choice for cheap non-critical items with a spare available, and it is a problem only when it happens by accident.