For a fleet, maintenance isn’t something you do when a truck breaks down — it’s something you schedule so it doesn’t. A consistent, mileage-based preventive maintenance (PM) schedule is the single most effective way to cut downtime, extend vehicle life, and avoid the surprise repair bills that wreck a month’s budget. Here’s a practical guide to what to check and roughly when.
One important note up front: exact intervals vary by vehicle type (light-duty gas vans vs. heavy-duty diesel trucks), load, and duty cycle. Always follow your manufacturer’s recommended schedule — use the ranges below as a general planning framework, not gospel.
Why a Mileage-Based Schedule Beats “Fix It When It Breaks”
Reactive maintenance always costs more. A worn part that’s caught during a scheduled service is a quick, planned fix; the same part left to fail becomes a roadside breakdown, a tow, lost delivery time, and an idle driver. A PM schedule turns unpredictable emergencies into predictable, budgetable maintenance — and keeps your vehicles DOT- and BIT-ready in the process.
Every Trip: Daily Pre-Trip Checks
The cheapest maintenance is what your drivers catch before rolling out. A quick daily walkaround should cover:
- Tire pressure and condition
- Lights and signals
- Fluid leaks under the vehicle
- Brakes and air pressure (for air-brake vehicles)
- Mirrors, wipers, and horn
Every 3,000–7,000 Miles: Routine Service (light-duty)
For gas vans and light-duty vehicles, this is your regular touchpoint:
- Oil and oil-filter change
- Tire rotation and pressure check
- Top off fluids (coolant, washer, brake, power steering)
- Visual inspection of belts, hoses, and battery
Heavy-duty diesels typically run longer oil intervals (often 15,000–25,000+ miles) — follow the engine maker’s spec.
Every 15,000–25,000 Miles: Wear-Item Inspection
- Brake pads, rotors, and (for air brakes) linings and drums
- Tire tread depth and alignment
- Air and cabin filters
- Battery load test and terminal cleaning
- Suspension and steering components
Every 30,000–50,000 Miles: Major Service
- Transmission fluid and differential service
- Coolant flush
- Fuel system and injector service (especially diesels)
- Serpentine/timing belt inspection or replacement
- Full brake-system service as needed
Seasonal and Compliance Checks
Layer these on top of the mileage schedule:
- Summer: cooling system, A/C, tires, and batteries before Central Valley heat sets in
- Winter: batteries, wipers, tires, and heating
- Compliance: DOT annual inspection and California BIT 90-day inspections — keep records current and audit-ready
Keep It Documented
A PM schedule is only as good as your records. Log every inspection and service by vehicle and mileage. Good documentation not only tells you what’s due next — it’s exactly what the CHP wants to see during a BIT terminal inspection, and it protects the resale value of your fleet.
Let ADM Handle It On-Site
Staying on a PM schedule across a whole fleet is a lot to manage — which is why ADM Auto Services runs preventive maintenance programs on-site at your yard across the Bay Area and Central Valley. We service your vehicles on schedule, keep your records inspection-ready, and handle repairs as they come up, so your trucks spend more time working and less time in the shop.
Ready to build a PM program for your fleet? Call ADM Auto Services at 510.552.4926.
Jermiah King is the founder of ADM Auto Services. A trained diesel technician, he brings deep hands-on experience from the oil field and advanced manufacturing industries, including robotics and PLC work. After relocating to California in 2017, he founded ADM Auto Services to pursue what he loves most — keeping fleets running with expert, reliable vehicle service across the Bay Area and Central Valley.
