Fleet Maintenance Schedule: A Mile-by-Mile Diesel Service Calendar

Fleet uptime starts with a maintenance calendar that everyone in the shop trusts. The schedule below is a starting point for HD diesel trucks running typical commercial duty. Adjust intervals for severe-duty (off-road, towing, dusty) by cutting them roughly in half.

Every 5,000 miles

• Walk-around: lights, leaks, tires, mirrors
• Check fluids: engine oil level, DEF, coolant, washer
• Brake pad visual

Every 15,000 miles

• Engine oil and oil filter change (HD diesel spec)
• Fuel filter replacement
• Air filter inspection (replace if dusty environment)
• Tire rotation

Every 30,000 miles

• Transmission fluid level/check
• Differential oil level
• DEF tank inspection
• Battery load test
• U-joint and driveline grease

Every 60,000-100,000 miles

• Coolant flush and refill
• Transmission fluid and filter change
• Differential fluid change
• Belt and hose inspection
• EGR system inspection and clean as needed

Track everything

If you run more than two trucks, a notebook stops working at 30,000 miles. The [Fleet Maintenance Tracker](https://gas-and-diesel-engine-equipment-guide.com#eeg-fleet) logs service history per vehicle and exports as JSON for backup or CMMS import — all stored on your device.