The most practical way to compare these two is not by what they do but by what each requires before it can produce anything at all, because that is what determines which one a given site can actually start on Monday. Preventive needs one thing. Predictive needs four, and a programme missing any of them produces readings nobody acts on. Laying the prerequisites side by side also explains, without any argument about philosophy, why almost every site builds the preventive programme first.
What preventive needs: a list and a decision
An asset list and an interval on each, chosen by somebody competent for that equipment. That is it. No instrumentation, no baseline, no specialist interpretation. Which is why a site with nothing can have a working preventive programme covering its critical equipment within a week, and why it remains the base layer even at sites with sophisticated monitoring.
What predictive needs: four things, all of them
Instrumented assets chosen for consequence. A baseline period measuring normal operation, because a reading means nothing on its own. Somebody who can distinguish a meaningful change from noise. And a route from a finding into scheduled work. Three out of four produces a dashboard, and a dashboard nobody acts on is the most common outcome of a predictive project.
Why the order is almost always preventive first
The preventive programme produces the thing the predictive decision needs: a record of what has actually failed at your site, how often, and what it cost. Choosing what to instrument without that record is choosing with no evidence, and it is why so many monitoring installations end up on the assets that were easiest to instrument rather than the ones that mattered.
Questions people ask about predictive maintenance vs preventive maintenance
Can a site skip preventive and go straight to predictive?
On a handful of critical assets, occasionally, where the failure mode is well understood. Across a site, no: predictive covers only what is monitored, and everything else would then have no strategy at all.
How long is a baseline period?
Long enough to cover the asset's normal range of operation, including the seasonal or duty variation it actually sees. Rushing it produces thresholds that alarm on normal behaviour, and trust lost early is hard to recover.
Is a maintenance record a prerequisite for predictive?
Not formally, and in practice it is the thing that makes the investment decision defensible. Without it, which assets to monitor is a matter of opinion.