2016 Mercedes-Benz Metris Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2016 Mercedes-Benz Metris is crucial for optimal engine performance, fuel efficiency, and longevity. Spark plugs are not "one size fits all." Key factors like heat range and electrode material play a significant role.

Heat Range: This refers to the plug's ability to dissipate heat. A plug that's too "hot" (dissipates heat slowly) can lead to pre-ignition and engine damage, while a plug that's too "cold" (dissipates heat quickly) can foul up with carbon deposits. Your Metris's 2.0L turbocharged engine requires a specific heat range to cope with its combustion temperatures.

Electrode Metal:

• Iridium: This is the most common and recommended material for modern engines, including your Metris. Iridium plugs offer superior durability and a finer electrode tip, leading to a more consistent, powerful spark and extended service life. They are generally rated for 100,000 miles or more, though Mercedes-Benz specifies a 60,000-mile interval for the Metris.
• Platinum: Platinum plugs also offer good durability and a longer lifespan than copper, typically around 60,000 miles. They are often used as OEM in many vehicles.
• Copper: While excellent conductors, copper electrodes wear quickly and are not suitable for the extended service intervals and hot combustion temperatures of your Metris's engine. Copper plugs are usually found in older, less demanding applications.

How to gap a spark plug

While many modern iridium plugs come pre-gapped, it's always a good idea to verify the gap, especially with shipping. The 2.0L M274 engine in your Metris typically requires a gap between 0.031-0.035 inches (0.8-0.9 mm). You'll need a wire-type spark plug gapping tool, as ramp-style gappers can damage fine-wire electrodes.

1. Measure: Carefully slide the correct thickness wire gauge between the center and ground electrodes. There should be a slight drag.
2. Adjust (if needed): If the gap is too small, use the gapping tool's leverage hole to gently pry the ground electrode outwards. If the gap is too large, gently tap the ground electrode on a clean, hard surface to close it slightly. Be extremely careful not to bend or damage the delicate iridium tip.
3. Re-measure: Always re-measure to confirm the correct gap.

Replacement procedure tips

Replacing spark plugs on your 2016 Mercedes-Benz Metris with the M274 engine is a straightforward but delicate process.

1. Coil-on-Plug Removal: Your Metris uses a coil-on-plug (COP) ignition system. Each spark plug has its own ignition coil mounted directly on top. To access the plugs, you'll need to carefully disconnect the electrical connector from each coil and then remove the coil retaining bolt (usually a Torx bolt). Gently twist and pull the coil upward to remove it. Be mindful of the rubber boot, as it can sometimes stick to the spark plug.

2. Anti-Seize Debate: There's ongoing debate regarding the use of anti-seize compound on spark plug threads. Most modern spark plugs, especially those with nickel-plated shells, do not require anti-seize. In fact, using it can alter torque readings, leading to overtightening and potential damage to the cylinder head threads. Mercedes-Benz generally advises against it for their engines. Follow the spark plug manufacturer's recommendations or your Mercedes-Benz service manual.

3. Dielectric Grease on Boots: Applying a small amount of dielectric grease inside the rubber boot of the ignition coil (where it contacts the spark plug ceramic) is highly recommended. This helps to seal out moisture, prevents the boot from sticking to the plug, and eases future removal. It also improves electrical insulation.

4. Torque is Key: Always use a torque wrench to tighten spark plugs to the specified value (17-20 lb-ft / 23-27 Nm). Overtightening can damage the plug or the cylinder head threads, while undertightening can lead to combustion gas leakage, overheating, and misfires.

Known issues

Fortunately, there are no widespread "known issues" specific to spark plug failure or replacement on the 2016 Mercedes-Benz Metris 2.0L M274 engine, such as the infamous broken 2-piece plugs on certain Ford 3-valve engines.

Problems, if they arise, are typically due to neglected maintenance, incorrect plug choice, improper gapping, or incorrect installation (i.e., not using a torque wrench).

Need plugs replaced? Find a shop on Repairius.