7DCT300 Oil Change: DIY Steps & Service Tips

How to perform a 7DCT300 Oil Change?

When it comes to keeping your Mercedes-Benz GLA X156 performing at its best, one of the most critical yet often overlooked tasks is the 7DCT300 oil change. The 7G-DCT (also referred to as 7DCT300) is known for smooth shifting and efficient power delivery, but it relies heavily on clean, high-quality transmission fluid.

Over time, fluid degrades due to heat and contaminants, leading to slipping, hard shifts, or even costly transmission damage. Regular oil changes not only ensure driving comfort but also extend the life of the gearbox.

For a complete overview of all service intervals, A/B maintenance schedules, and preventive care, see our Mercedes Maintenance and Service Guide.

Why the 7DCT300 Oil Change Matters

– Preserves performance : Fresh fluid ensures smooth gear changes.
– Prevents overheating : Old oil loses its cooling and lubricating properties.
– Extends transmission life : Regular changes help avoid costly rebuilds.
– Protects against wear : Debris and contaminants are flushed out.

Step-by-Step: How to Perform a 7DCT300 Oil Change

This step-by-step guide will take you through the process of changing the 7G-DCT oil in your GLA, ensuring your transmission remains in top shape and your driving experience remains nothing short of extraordinary. Get ready to dive into the details and give your Mercedes the care it deserves!

STEP 1 : Deposit

1. Remove the air filter housing.
2. Place absorbent cloths in the area under the oil filter cover (5). See image below

3. Remove the oil filter cover (5).
4. Replace the seal ring (11) on the oil filter cover (5).
5. Replace the oil filter cartridge (10).
6. Install the oil filter cover (5).
7. Remove the absorbent cloths from the area under the oil filter cover (5).
8. Remove the lower part of the rear engine compartment cover. See image below

STEP 2 : DRAIN

1. Unscrew the drain plug with permanent magnet (2) and drain the transmission oil.

Close-up of 7DCT300 transmission drain plug with oil draining into container during service. — **Mercedes 7DCT300 drain plug location and oil draining**

STEP 3 : Deposit

1. Remove the oil pan (3).

Oil pan and filter removed from Mercedes 7DCT300 dual-clutch transmission for fluid change. — **Mercedes 7DCT300 oil pan and filter removal**

2. Remove the oil filter (4).

STEP 4 : Clean

1. Clean and inspect the drain plug with permanent magnet (2) for damage.

– If the drain plug with permanent magnet (2) shows signs of damage, replace the drain plug with permanent magnet (2).

STEP 5 : Install

1. Install a new oil filter (4).
2. Screw in the drain plug with permanent magnet (2) and a new seal ring (12) tightly.
3. Install the oil pan.
4. Remove the safety pin (14).
5. Remove the oil dipstick tube cap (8).

STEP 6 : Filling

1. Pre-fill the dual-clutch transmission (1) with new transmission oil through the oil dipstick tube (9).

STEP 7 : Check

1. Check and adjust the transmission oil level in the dual-clutch transmission (1).
2. Check for damage to the o-ring (13) on the oil dipstick tube cap (8).
– If the o-ring (13) on the oil dipstick tube cap (8) is damaged, replace the o-ring (13) on the oil dipstick tube cap (8).

STEP 8 : Install

1. Install the oil dipstick tube cap (8).
2. Install the new safety pin (14) in the oil dipstick tube cap (8).

Service Interval for 7G-DCT (7DCT300)

– Standard: Every 40,000–60,000 miles (60,000–100,000 km).
– Severe Conditions: Service more frequently (towing, stop-and-go traffic, extreme heat).
– Early Warning Signs: Hard shifts, slipping, or unusual noises indicate earlier fluid change.

Always confirm in your owner’s manual, as service intervals vary by model.

Is Mercedes Transmission Fluid Lifetime?

Mercedes-Benz does not consider transmission fluid to be lifetime. Even if some fluids are marketed as such, they degrade over time.

– Recommended Change: Every 40,000–60,000 miles.
– Driving Conditions: Harsh use shortens fluid life.
– Fluid Quality: Old fluid loses lubrication and cooling efficiency.
– Manufacturer Guidelines: Always follow official Mercedes specifications for fluid type and service.

Following these intervals helps prevent premature wear and ensures a smooth, long-lasting transmission.

Symptom – Cause & Fix Table

Symptom	Likely Cause	Fix
Jerky or delayed shifting	Old / degraded fluid	Perform oil change with OEM fluid
Transmission overheating	Low or contaminated fluid	Drain and refill, inspect cooling system
Warning light on cluster	Service interval reached	Reset after oil change
Metallic shavings in oil	Excessive internal wear	Replace oil, inspect transmission

Maintenance Tips for 7DCT300 Owners

– Use Mercedes-approved ATF only.
– Stick to manufacturer intervals (40–60k miles).
– Pair transmission service with Service B maintenance.
– Record every oil change for resale value and warranty compliance.
– If DIY, always torque bolts to spec and double-check fluid level.

FAQs

Q: Can I change the 7DCT300 oil myself?
Yes, if you have the right tools and follow the procedure carefully. However, professional service is recommended for accuracy.

Q: What type of oil is used in the 7DCT300?
Always use OEM-specified dual-clutch transmission fluid. Check your manual for the correct spec.

Q: Do I need to reset anything after service?
Yes, reset the transmission service interval using STAR Diagnostic/XENTRY or an OBD-II tool.

Q: What happens if I delay the oil change?
You risk hard shifting, overheating, and costly transmission repair.

Author

Written by Mercedes Expert
With years of hands-on experience diagnosing and repairing Mercedes-Benz systems, he brings technical depth and practical case studies to help car owners, technicians, and enthusiasts troubleshoot complex automotive issues. His work focuses on clear repair guides, OEM-level procedures, and knowledge-sharing to empower both professionals and drivers.
Last Updated: September 2025