Diesel Maintenance Schedule Generator

A diesel PM schedule in 2026 follows three tiers: PM-A (oil and filters) every 10,000–15,000 miles or 250–500 hours, PM-B (fuel filters) every 10,000–25,000 miles, and PM-C (valve adjustment) every 100,000–300,000 miles by engine. Severe-duty and idle-heavy use cuts intervals 30–50%. Use the generator above with engine brand, mileage, hours, and duty cycle. Below: what each service includes and what it costs in 2026.

PM-A Service — Oil, Filters, and Inspection

PM-A is your bread-and-butter service. Skip it and everything else fails early.

What PM-A Includes

Task	Linehaul Interval	Severe/Idle Interval
Engine oil and filter change	15,000 mi / 500 hrs	8,000–10,000 mi / 250–300 hrs
Fuel filter (primary)	Inspect at PM-A	Inspect at PM-A
Coolant test (refractometer)	Every PM-A	Every PM-A
Belt and hose inspection	Every PM-A	Every PM-A
Air filter inspection	Every PM-A	Every PM-A
DEF level check	Every PM-A	Every PM-A
Grease all fittings	Every PM-A	Every PM-A
Drain water separator	Every PM-A	Every PM-A

Oil Specifications by Engine

Engine	Recommended Oil	Capacity (approx.)	Filter Part (Reference)
Cummins ISX15/X15	CES 20086 (CK-4 15W-40)	11 gal (with filter)	Fleetguard LF14000NN
Detroit DD15	DFS 93K222 (CK-4 15W-40)	10.5 gal	Detroit A4721800809
PACCAR MX-13	CK-4 15W-40	10 gal	PACCAR 2516824
6.7L Cummins	MS-11106 (CK-4 15W-40)	12 qt	Mopar 68191349AA
6.7L Powerstroke	WSS-M2C171-F1 (CK-4)	13 qt	Motorcraft FL-2016
6.6L Duramax L5P	dexos2 (CK-4 equivalent)	10 qt	ACDelco PF2232

Use oil that meets the engine manufacturer’s spec — not just “diesel oil.” CK-4 is the current standard for 2017+ on-highway diesels. FA-4 (lower viscosity, 10W-30) is approved by Cummins and Detroit for fuel economy but check your warranty requirements before switching.

PM-A Cost Estimates (2026)

Vehicle Class	Parts	Labor	Total
Pickup diesel	$80 – $150	$80 – $150	$160 – $300
Class 6–7	$120 – $220	$120 – $180	$240 – $400
Class 8	$150 – $280	$150 – $250	$300 – $530

Truck-stop PM-A on Class 8 equipment runs $200–$350 when oil is purchased in bulk. Dealer PM-A on a pickup runs $250–$400.

PM-B Service — Fuel System Maintenance

Fuel quality is the number one killer of diesel injection systems. PM-B focuses on fuel filtration and water separation.

Task	Linehaul Interval	Severe Interval
Primary fuel filter	25,000 mi / 750 hrs	10,000 mi / 300 hrs
Secondary fuel filter	25,000 mi / 750 hrs	10,000 mi / 300 hrs
Fuel/water separator drain	Every PM-A	Every PM-A
Fuel tank inspection (water, algae)	Annually	Every 6 months
Fuel line inspection (chafing, leaks)	Every PM-B	Every PM-B

Fuel Filter Part Numbers

Engine	Primary Filter	Secondary Filter
Cummins ISX15	Fleetguard FS10915	Fleetguard FF5825NN
Detroit DD15	Detroit A0000901551	Detroit A4720700888
6.7L Cummins	Mopar 68197867AA	Mopar 68157291AA
6.7L Powerstroke	Motorcraft FD-4615	Motorcraft FD-4617
6.6L Duramax L5P	ACDelco TP1015	ACDelco TP1018

Fill the new filter with clean diesel before installation on common-rail systems to prevent dry-start scoring. Torque filter housings to spec — over-tightening cracks the housing on Fleetguard FS series caps.

PM-B cost: $80–$200 in parts, $60–$120 labor. Cheap insurance against a $5,000 injector job.

PM-C Service — Valve Adjustment and Major Inspection

PM-C is the big service that most drivers skip until the engine runs rough. Don’t.

Task	Heavy-Duty Interval	Pickup Interval
Valve lash adjustment	300,000 mi / 10,000 hrs	100,000 – 135,000 mi
Injector height/lash check	With valve adjustment	With valve adjustment
Compression test (spot check)	Every 2nd PM-C	At 200,000+ mi
Turbo inspection (shaft play, VGT)	Every PM-C	Every PM-C
Aftertreatment inspection	Every PM-C	Every PM-C
Transmission fluid check	Every PM-C	Per OEM schedule
Differential fluid check	Every PM-C	Per OEM schedule

Valve Adjustment Specs

Engine	Intake Lash	Exhaust Lash	Notes
Cummins ISX15	0.014” (cold)	0.027” (cold)	Jake brake on exhaust
Detroit DD15	0.015” (cold)	0.030” (cold)	Use feeler gauge, engine cold
6.7L Cummins	Hydraulic (no adjustment)	Hydraulic	Check rocker box at 100k
6.7L Powerstroke	Hydraulic	Hydraulic	No manual adjustment
6.6L Duramax L5P	Hydraulic	Hydraulic	No manual adjustment

Class 8 engines with mechanical valve trains need adjustment. Running 50,000 miles over interval causes burnt valves, lost power, and hard starting. PM-C labor on an ISX15: 6–10 hours ($870–$1,750).

Duty Cycle Adjustments

The generator above adjusts intervals based on your duty cycle. Here is why each matters:

Linehaul (Highway)

Best-case scenario for engine life. Sustained operating temps burn off fuel dilution from regens. Oil stays cleaner longer. Use standard OEM intervals.

City / P&D (Pickup and Delivery)

Frequent stops, short trips, moderate idle. Cut oil change interval by 20%. Regens may not complete on short routes — monitor soot load. Fuel filter interval: every 15,000 miles.

Severe (Dust, Construction, Mining)

High dust loads clog air filters fast. Cut oil interval to 10,000 mi / 300 hrs. Replace air filter at every PM-A (not just inspect). Fuel filter every 10,000 miles. Coolant test every PM-A — overheating risk is higher.

Idle-Heavy (Refrigerated, PTO, Utility)

Worst case for oil life. Idle does not generate enough heat to burn off fuel dilution from passive regens. Oil change: 8,000 mi / 250 hrs maximum. Monitor oil level — it rises from fuel dilution. Run oil analysis every PM-A.

Oil analysis costs $25–$40 per sample (Blackstone, Polaris Labs). It tells you if your interval is right before you damage bearings.

Annual and Mileage-Based Services

Beyond PM-A/B/C, these services follow calendar or mileage triggers:

Service	Interval	Cost Range
Coolant exchange	300,000 mi / 5 years	$150 – $400
DEF filter	150,000 mi / 4,500 hrs	$80 – $200 (parts) + $60 – $120 (labor)
DPF ash cleaning	250,000 – 400,000 mi	$800 – $1,400
Transmission service	250,000 – 500,000 mi	$300 – $800
Differential fluid	250,000 – 500,000 mi	$150 – $400
Turbo actuator calibration	300,000 mi or as needed	$200 – $500
EGR valve cleaning	200,000 mi or when codes appear	$300 – $800
Battery test/replace	3 – 5 years	$200 – $400 (pair)
Belt replacement	100,000 – 150,000 mi	$80 – $250

Coolant Maintenance — Often Ignored, Always Expensive

Test coolant at every PM-A with a refractometer. Target freeze point: -34°F for 50/50 mix. Supplemental coolant additive (SCA) level on conventional coolant: 1.5–3.0 units per gallon.

Test Result	Action
Freeze point above -20°F	Add concentrate or exchange
pH below 7.5	Exchange coolant
SCA below 1.5 units	Add SCA or switch to ELC
Oil sheen on surface	Head gasket or oil cooler leak — diagnose immediately
Rust color	Exchange and flush system

Cummins ISX15 holds 11 gallons of coolant. Full exchange with Fleetguard ES Compleat: $120–$200 in coolant plus labor. ELC (extended life coolant) like Fleetguard ES Compleat Organic lasts 300,000 miles between exchanges on Class 8.

DEF System Maintenance

DEF quality matters. Contaminated DEF crystallizes in the pump and doser, causing $800–$2,000 repairs.

• Use API-certified DEF (ISO 22241)
• Store DEF between 12°F and 86°F
• DEF shelf life: 12 months in optimal storage, 6 months in heat
• Replace DEF filter at 150,000 miles (Detroit A0001400078, Cummins equivalent varies)
• Clean DEF tank if crystals form at the pickup screen

DEF consumption averages 2–3% of diesel consumption. A truck using 150 gallons of diesel per day uses roughly 3–4.5 gallons of DEF.

Air Filtration and Intake System

Duty Cycle	Air Filter Interval	Restriction Limit
Linehaul	50,000 – 75,000 mi	Replace at 25 in H₂O restriction
City/P&D	30,000 – 50,000 mi	Replace at 20 in H₂O
Severe/dust	10,000 – 20,000 mi	Replace at 15 in H₂O
Idle-heavy	25,000 – 40,000 mi	Inspect every PM-A

A clogged air filter causes high exhaust temps, incomplete regens, and turbo overspeed. Fleetguard AF25276 (ISX15) costs $45–$75. Five minutes to change, saves thousands in aftertreatment damage.

Building a Maintenance Log

Track these numbers at every service:

1. Date and odometer
2. Engine hours (if equipped)
3. Oil type and filter part number
4. Fuel filter part numbers
5. Any fault codes cleared
6. Oil analysis results (if taken)
7. Coolant test results
8. Technician name and shop

A maintenance log adds resale value and catches interval drift before it causes failures. A dated spreadsheet or bound logbook works — record every PM-A, filter change, and oil analysis result in one place.

Cost Per Mile — What PM Actually Costs

Vehicle Class	Annual Miles	Annual PM Cost	Cost Per Mile
Class 8 linehaul	100,000	$3,500 – $5,500	$0.035 – $0.055
Class 8 severe	80,000	$5,000 – $8,000	$0.063 – $0.100
Pickup (personal use)	15,000	$600 – $1,200	$0.040 – $0.080
Pickup (work/tow)	25,000	$1,000 – $2,000	$0.040 – $0.080

These numbers include PM-A/B/C services only — not repairs. Budget an additional $0.03–$0.05/mile for unplanned repairs after 300,000 miles.

FAQ

How often should I change oil in a diesel truck?

Linehaul Class 8: every 15,000 miles or 500 hours. Severe duty: every 10,000 miles or 300 hours. Idle-heavy: every 8,000 miles or 250 hours. Pickup diesels: every 7,500–10,000 miles or per OEM guide.

What is the difference between PM-A, PM-B, and PM-C?

PM-A is basic oil and filter service with inspections. PM-B adds fuel filter replacement. PM-C is major service including valve adjustment (on mechanical valve train engines), compression checks, and aftertreatment inspection.

Can I extend oil change intervals with synthetic oil?

CK-4 synthetic oils (Shell Rotella T6, Mobil Delvac 1 ESP) can support slightly longer intervals with oil analysis confirmation. Do not exceed OEM maximum without lab data showing acceptable wear metals and viscosity.

How often should fuel filters be changed on a diesel?

Every 25,000 miles for linehaul, every 10,000 miles for severe duty. Always replace both primary and secondary filters at the same time. Never run a diesel engine without both filters installed.

When does a diesel need valve adjustment?

Class 8 mechanical valve train engines: every 300,000 miles or 10,000 hours. Pickups with hydraulic lifters (6.7L Cummins, Powerstroke, Duramax): no manual adjustment, but inspect rocker components at 100,000 miles.

How much does a Class 8 PM service cost?

PM-A: $300–$530. PM-B (add fuel filters): $380–$650. PM-C (add valve adjustment): $1,250–$2,400. Annual total for a well-maintained linehaul truck: $3,500–$5,500.

Should I use oil analysis?

Yes, especially after 200,000 miles or if running extended drain intervals. A $30 oil sample catches bearing wear, fuel dilution, and coolant intrusion before they cause catastrophic failure.

What happens if I skip diesel maintenance?

Shortened engine life, failed regens, clogged DPF, injector failure from fuel contamination, turbo damage from oil starvation, and voided warranty. A skipped $300 PM-A leads to a $15,000 engine job.

Sources

• Cummins Operation and Maintenance Manual OMS4020 (2025 revision) — ISX15/X15 oil, fuel filter, and valve adjustment intervals
• Detroit Diesel DD Platform Operator’s Manual — PM-A/B/C service schedules and fluid specifications
• PACCAR MX-13 engine maintenance schedule — filter part numbers and severe-duty interval adjustments
• Ford 6.7L Powerstroke scheduled maintenance guide — oil capacity, filter specs, and DEF service intervals
• GM Duramax L5P owner’s manual supplement — CK-4 oil requirements and fuel filter replacement mileage
• ATA Recommended Practices RP 334 — severe-duty interval reduction factors for idle-heavy and dust environments

Related Reading

• Diesel preventive maintenance schedule by engine — PM-A, PM-B, and PM-C tasks mapped to Cummins, Detroit, and pickup platforms
• Fuel filter service intervals — primary and secondary replacement mileage for linehaul vs severe duty
• Engine hours vs miles for diesel service — when hour meters should drive your oil change interval instead of odometer
• How to read diesel oil analysis — wear metals and fuel dilution that justify shortening PM intervals
• Winter diesel maintenance checklist — seasonal additions to your PM schedule for cold-climate operation