Mercedes CLK320 Service Intervals: W208 & W209 Maintenance Guide

Keep your Mercedes CLK320 running like the luxury coupe it is with this comprehensive maintenance schedule based on factory specifications.

The Mercedes-Benz CLK320 pairs elegant styling with the reliable M112 V6 engine. Whether you own a W208 (1998-2002) or W209 (2003-2009) generation, following the proper service intervals ensures years of trouble-free driving. This guide covers the naturally aspirated 3.2L V6 models including the coupe and cabriolet variants.

Service Interval Overview

Mercedes uses two service types (A and B) that alternate every 10,000 miles:

• Service A: Oil change, inspections (every 10k, 30k, 50k miles)
• Service B: More comprehensive (every 20k, 40k, 60k miles)

Engine Oil Service

Interval: Every 10,000 Miles or 1 Year

The M112 V6 engine requires quality synthetic oil:

• Capacity: 7.5 quarts (with filter change)
• Specification: MB 229.5 or 229.51 (full synthetic)
• Viscosity: 5W-40 or 0W-40
• Filter: Mann HU 718/5X or OEM

DIY Oil Change Procedure

1. Warm engine to operating temperature
2. Remove underbody panel (if equipped)
3. Remove drain plug (13mm hex) - watch for hot oil
4. Remove oil filter housing cap (74mm 14-point socket)
5. Replace O-rings on filter cap
6. Install new filter and tighten cap to 25 N·m
7. Install drain plug with new crush washer, torque to 30 N·m
8. Add 7.5 quarts of specified oil
9. Start engine, check for leaks, verify level
10. Reset service indicator

Transmission Service

Interval: Every 40,000 Miles

The 5-speed automatic (722.6) benefits from regular fluid changes:

• Fluid: Mercedes ATF 134 (NOT Dexron)
• Capacity: 9.5 quarts total (5-6 quarts in pan)
• Filter: Replace with gasket
• Method: Pan drop and refill, or full flush

Note: These transmissions are marketed as "sealed for life" but fluid degradation causes harsh shifting. Regular changes prevent costly repairs.

Coolant Service

Interval: Every 30,000 Miles or 3 Years

• Type: Mercedes MB 325.0 (blue coolant)
• Capacity: 10.5 quarts
• Mix: 50/50 with distilled water

Procedure: Drain radiator and block, flush with distilled water, refill with proper mix. Bleed air from system using bleed screws.

Brake Fluid Service

Interval: Every 20,000 Miles or 2 Years

• Specification: DOT 4+ (MB 331.0)
• Capacity: 1.5 quarts for complete flush

Brake fluid absorbs moisture over time, lowering boiling point and causing corrosion. Use pressure bleeder or two-person method. Start at furthest caliper (right rear).

Spark Plug Replacement

Interval: Every 100,000 Miles

The M112 uses 12 spark plugs (two per cylinder):

• Type: NGK BKR6EKUB or Bosch F8DPP33
• Gap: 0.039 inches (1.0mm)
• Torque: 22 N·m (16 ft-lb)

Procedure: Remove engine covers, ignition coils, then spark plugs. Apply anti-seize to threads. Replace coils if old or showing signs of failure.

Air Filter Replacement

Interval: Every 20,000 Miles (Inspect Every 10k)

• Part: Mann C 32 191 or OEM
• Location: Left side of engine bay

Cabin Filter Replacement

Interval: Every 20,000 Miles

• Part: Mann CU 2736 or OEM
• Location: Behind glovebox

Fuel Filter Replacement

Interval: Every 60,000 Miles

Located under the vehicle near the fuel tank. Relieve fuel pressure before removing. Replace sealing rings.

Differential Service

Interval: Every 40,000 Miles

• Fluid: Hypoid gear oil SAE 75W-85 (MB 235.7)
• Capacity: 1.3 quarts

Major Service Schedule Summary

Resetting Service Indicators

W208 (1998-2002)

1. Turn key to position 2 (don't start)
2. Press trip odometer button twice within 4 seconds
3. Turn key off

W209 (2003-2009)

1. Turn key to position 1
2. Press and hold the phone button and OK button simultaneously
3. Scroll to ASSYST PLUS and select
4. Select Full Service and confirm

DIY Cost Savings

Performing basic maintenance yourself saves significant money:

• Oil change: DIY $60 vs Dealer $200+
• Cabin filter: DIY $20 vs Dealer $150+
• Brake fluid flush: DIY $30 vs Dealer $250+
• Transmission service: DIY $150 vs Dealer $500+

Last Updated: 2026-03-15