Seven numbers tell you whether a maintenance program is working: PM compliance, the planned-to-unplanned ratio, cost per mile or hour, time between failures and time to repair, downtime hours, repeat-repair rate, and the roadside inspection pass rate. None of them needs software. They need a unit list, work orders with the hours or miles written on them, and a downtime log someone actually fills in. Here is each one with its formula, what it takes to collect, and what moves it.
Before Any KPI: Three Records You Must Keep
- A unit list with unit number, VIN or serial, year, make, model, engine, and the PM interval that applies to it.
- A work order for every job, including your own oil changes and the roadside jump-start, with the date, the odometer or hour-meter reading, whether it was planned (PM, scheduled repair) or unplanned (breakdown, DVIR defect, roadside), the parts, the labor, and the cost.
- A downtime log: the time the unit became unavailable and the time it went back in service. A column on the work order is enough.
Miss the hours-or-miles reading on the work order and half of the KPIs below cannot be computed. That is the one discipline to enforce.
The 7 KPIs
1. PM compliance
Formula: PMs completed within their window ÷ PMs that came due, over the period.
Window: decide it once. A common choice is the interval plus 10 percent, so a 250-hour PM counts as on time up to 275 hours, and a 15,000-mile oil change up to 16,500.
Collect it: a sheet with one row per unit: last PM reading, interval, due reading, current reading. Count the units past due at month end and the PMs done late during the month.
What moves it: scheduling the PM before it is due rather than when the unit happens to be free, and a service provider who comes to the yard so the unit does not have to be spared for a day.
2. Planned-to-unplanned ratio
Formula: planned maintenance hours (or dollars) ÷ total maintenance hours (or dollars). Track both versions if you can; the dollar version is the one that catches expensive breakdowns.
Collect it: the planned/unplanned checkbox on the work order. Sum each column monthly.
What moves it: a rising ratio means the inspection part of the PM is catching things before they fail. If PM compliance is high but the ratio is not improving, the PM checklist is being pencil-whipped.
3. Cost per mile, or cost per hour on equipment
Formula: total maintenance cost for the unit over the period ÷ miles (or engine hours) run in the period. Include parts, labor, outside services, tires if you want a fully loaded number, and the emergency premiums. Exclude fuel and DEF.
Collect it: the sum of work-order cost per unit, divided by the difference between the reading at the start and end of the period. This is why the reading goes on every work order.
What moves it: compare a unit to itself over time and to its siblings of the same class and age, not to a published number. A unit whose cost per hour is climbing while its siblings are flat is telling you it is time to decide between a major repair and replacement. Duty cycle matters: a skid steer eating red-clay dust at a Sand Springs pad site will not match one doing landscape work in Jenks, and it should not.
4. MTBF and MTTR
Mean time between failures: operating hours (or miles) in the period ÷ number of unplanned failures. Higher is better.
Mean time to repair: total downtime hours from unplanned failures ÷ number of unplanned failures. Lower is better.
Collect it: count the unplanned work orders per unit, and use the downtime log for the repair hours. Include parts wait and transport time in MTTR; that is the point of it.
What moves it: MTBF moves with PM quality. MTTR moves with how fast a mechanic gets to the unit and whether the right parts are on the truck. A unit that has to be trailered to a shop carries the loading and hauling time in its MTTR whether or not anyone writes it down.
5. Downtime hours
Formula: total hours unavailable ÷ scheduled available hours, per unit and for the fleet. Split it planned versus unplanned.
Collect it: the downtime log. Define scheduled hours honestly: a dump truck scheduled 10 hours a day, 5 days a week, has 50 available hours a week, and a PM done Saturday morning costs zero of them.
What moves it: moving maintenance into hours the unit was not going to work anyway, and cutting the unplanned column with the inspection items in the PM.
6. Repeat-repair rate
Formula: repairs on the same unit, same system, within a short window of a prior repair (30 days is a reasonable window) ÷ total repairs.
Collect it: a system column on the work order (brakes, electrical, cooling, hydraulics, aftertreatment, and so on). Sort by unit and system and look for pairs within the window.
What moves it: diagnosis instead of parts-swapping. A battery replaced three times in a year was never the problem; a charging fault or a parasitic draw was. A hydraulic hose that fails twice in the same spot has a rub point nobody fixed. Repeat repairs are the fastest way to evaluate a service provider.
7. Roadside inspection pass rate
Formula: roadside inspections with no vehicle violations ÷ total roadside inspections. Track out-of-service orders separately; one OOS is worth more attention than several minor violations.
Collect it: every roadside inspection report the driver hands in (which the driver is required to deliver to you, and which you must sign, return within 15 days if violations were found, and keep for 12 months under 49 CFR 396.9). Your carrier's inspection history is also visible in the FMCSA portal.
What moves it: brake stroke, lights, and tires, in that order. Those are what inspectors find. A pushrod stroke measurement and a lamp check at every A service, and a real annual inspection rather than a sticker, are what move this number.
Summary Table
| KPI | Formula | Source | Review |
|---|---|---|---|
| PM compliance | On-time PMs ÷ PMs due | PM schedule sheet | Monthly |
| Planned-to-unplanned | Planned hours or cost ÷ total | Work-order checkbox | Monthly |
| Cost per mile / hour | Maintenance cost ÷ miles or hours | Work orders with readings | Quarterly, per unit |
| MTBF / MTTR | Hours ÷ failures; downtime ÷ failures | Unplanned work orders, downtime log | Quarterly |
| Downtime hours | Hours down ÷ scheduled hours | Downtime log | Monthly |
| Repeat-repair rate | Repeats within 30 days ÷ total repairs | Work orders by unit and system | Quarterly |
| Roadside pass rate | Clean inspections ÷ inspections | Roadside reports, FMCSA portal | Every inspection |
A Monthly Routine That Takes an Hour
- Update the current reading for every unit (telematics export, or a walk with a clipboard).
- Flag units within a week of a PM due and schedule them.
- Total planned and unplanned hours from the month's work orders.
- List every unplanned event with its system and downtime hours. Look for repeats.
- Once a quarter, compute cost per mile or hour per unit and rank them. The top two or three are your replacement or overhaul conversation.
FAQ
Which KPI should a five-truck fleet start with?
PM compliance and the downtime log. Everything else is derived from those two habits.
Should I compare my numbers to industry benchmarks?
Compare a unit to itself over time and to your own similar units. Published benchmarks blend long-haul tractors with delivery vans and ignore duty cycle, climate, and age. Your trend is the useful signal.
Does a mobile mechanic change the numbers?
It changes MTTR and downtime hours directly, because the transport time disappears and the PM can happen when the unit was going to sit anyway. The record from each visit, with the reading on it, is what feeds the rest.
Need the PMs That Feed These Numbers?
Tulsa Fleet Repair is a mobile operation — the service truck comes to your yard, jobsite, or breakdown location anywhere within 120 miles of Tulsa, with 24/7 emergency response when a unit can't wait. Every visit leaves a written record with the unit number and reading. See preventive maintenance, then call (918) 925-9356 or request service online.
