2022 Mercedes-Benz Metris Spark Plug Type & Gap

Quick reference

Why the right plug matters

Using the correct spark plug for your 2022 Mercedes-Benz Metris is crucial for optimal engine performance, fuel efficiency, and longevity. The "right" plug isn't just about fitting in the hole; it's about heat range and electrode materials.

Heat Range: The heat range refers to the spark plug's ability to dissipate heat from the combustion chamber. A plug that's too "cold" (dissipates heat too quickly) can lead to carbon fouling, while a plug that's too "hot" can cause pre-ignition and engine damage. Mercedes engineers have specified the ideal heat range for the M274 engine, so sticking to OEM or equivalent aftermarket plugs is essential.

Electrode Metal: Modern Mercedes engines, including the M274 in your Metris, are designed for long-life iridium spark plugs. Iridium is an extremely hard and durable precious metal, allowing for very fine electrodes that produce a strong, consistent spark. This design contributes to improved fuel economy, reduced emissions, and extended replacement intervals compared to older platinum or copper plugs.

• Iridium: Standard for your Metris. Offers the longest lifespan and best performance.
• Platinum: A good alternative for older vehicles, but not typically specified for modern Mercedes engines.
• Copper: Excellent conductivity but very short lifespan. Rarely used in modern vehicles due to their rapid wear.

How to gap a spark plug

The spark plug gap is the distance between the center and ground electrodes. An incorrect gap can lead to misfires, reduced power, and poor fuel efficiency. While most modern iridium plugs come pre-gapped from the factory, it's always good practice to double-check, especially if you're using an aftermarket plug. The specified gap for your 2.0L Metris is 0.032 inches (0.8 mm).

To check the gap, use a wire-type spark plug gapping tool or a feeler gauge. Gently slide the appropriate gauge wire or blade between the electrodes. There should be a slight drag. If the gap is too small, you can carefully widen it by bending the ground electrode slightly with the gapping tool. If it's too wide, gently tap the ground electrode on a clean, hard surface to close the gap. Be extremely careful not to damage the delicate iridium center electrode.

Replacement procedure tips

The 2.0L M274 engine in your Metris features a coil-on-plug (COP) ignition system, meaning each spark plug has its own ignition coil directly mounted on top of it. This eliminates troublesome spark plug wires.

1. Preparation: Ensure the engine is cool before starting. Gather your tools, including a torque wrench, spark plug socket (typically 14mm thin-wall), extension, ratchet, and a magnetic or rubber-insert spark plug tool.
2. Coil Pack Removal: Carefully disconnect the electrical connector from each ignition coil. Then, unbolt the coil (if applicable; some just pull straight out) and gently pull it straight up to remove it from the spark plug well. Avoid yanking on the wires.
3. Spark Plug Removal: Use your spark plug socket with an extension to reach the plugs. Loosen them counter-clockwise. Be gentle to avoid cross-threading or breaking the plug.
4. Anti-Seize Debate: Mercedes-Benz, along with many other manufacturers, generally advises against using anti-seize on spark plug threads with modern plugs. The reason is that many new spark plugs have a special coating on the threads, and anti-seize can interfere with the torque readings, leading to over-tightening and potential cylinder head damage. Always refer to your vehicle's service manual or the spark plug manufacturer's instructions. If you opt to use anti-seize, it's critical to reduce the specified torque by about 10-20%.
5. Dielectric Grease: Apply a small amount of dielectric grease inside the spark plug boot (the part of the coil that connects to the plug). This helps lubricate the boot for easier installation and removal, and also helps seal out moisture, preventing corrosion and misfires.
6. Installation: Hand-thread the new spark plugs clockwise to ensure they don't cross-thread. Once finger-tight, use a torque wrench to tighten them to the specified 17.7 lb-ft (24 Nm). Over-tightening can damage the spark plug or cylinder head, while under-tightening can lead to blow-by or misfires.
7. Coil Pack Reinstallation: Reinstall the ignition coils, ensuring they are seated firmly over the spark plugs. Reconnect the electrical connectors.

Known issues

Fortunately, the 2.0L M274 engine in the Mercedes-Benz Metris does not have widespread, notorious spark plug related issues like the Ford 3-valve engine's design with two-piece plugs or specific GM engines with ionization-sensing coils. Sticking to the recommended service intervals and using the correct spark plugs will help keep your Metris running smoothly.

Need plugs replaced? Find a shop on Repairius.