Aftertreatment failures feel sudden but aren't — the components telegraph their condition in mileage and behavior long before the 5 MPH message. This schedule is what we hand fleet customers; it applies to any post-2010 diesel.
The schedule by component
| Component | Interval | Service | Skip it and… |
|---|---|---|---|
| DEF filter | 200k mi / 2 yrs | Replace ($40 part) | DEF pressure codes → pump strain |
| DEF tank | Annually | Inspect for crystallization/contamination | Quality faults, doser fouling |
| DPF | 300–400k mi (app-dependent) | Bake/clean service ($400–600) | Ash overload → $3,000+ replacement |
| NOx sensors | Expect 150–300k mi life | Replace on drift/failure | False SCR codes, misdiagnosis cascades |
| Doser valve | Inspect at DPF service | Clean or flow-test | Failed regens, DPF soot overload |
| EGR system | 200k mi inspection | Clean valve/cooler passages | Soot overproduction → DPF overload |
The cheap habits that multiply component life
- Buy sealed DEF from high-turnover sources; date the stock. Old DEF is a top-three derate cause.
- Highway miles weekly — trucks that never reach sustained temperature kill DPFs years early.
- Use CK-4 low-ash oil. Wrong oil is slow poison for DPFs.
- Read codes monthly, not at the lamp — aftertreatment faults are cheapest when caught as warnings.
Frequently Asked Questions
Is DPF cleaning worth it vs replacement?
Cleaning at $400–600 restores most DPFs to near-new flow at a fifth of replacement cost — at the right interval. Wait until the DPF is cracked or melted and cleaning is off the table. The interval is the whole game.
Do vocational trucks follow the same schedule?
Halve the DPF intervals for low-load duty cycles (mixers, refuse, delivery) — soot accumulates far faster without highway temperatures. DEF and sensor items stay mileage-based.