2019 Mercedes-Benz Metris Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2019 Mercedes-Benz Metris is critical for optimal engine performance, fuel efficiency, and longevity. The spark plug is responsible for igniting the air-fuel mixture in your engine's combustion chambers, and an incorrect plug can lead to a host of problems.

Heat Range: Spark plugs are designed with a specific "heat range," which refers to their ability to dissipate heat from the combustion chamber. A plug that is too "cold" (dissipates heat too quickly) can lead to fouling, while a plug that is too "hot" (dissipates heat too slowly) can cause pre-ignition and engine damage. The M274 engine in your Metris requires a specific heat range to operate efficiently and prevent issues.

Electrode Metal: The material used for the spark plug's electrodes also plays a significant role in its performance and lifespan. Modern vehicles, like your Metris, typically use long-lasting precious metal plugs:

• Iridium: This is the most common material for OEM plugs in newer vehicles. Iridium plugs offer exceptional durability and a very fine electrode tip, providing a strong, consistent spark for extended periods, usually 60,000-100,000 miles. Your Metris uses iridium plugs from the factory.
• Platinum: Platinum plugs offer good durability, typically lasting 40,000-60,000 miles. While not as long-lasting as iridium, they are a significant upgrade over copper.
• Copper: Copper plugs have a thicker electrode and are the least durable, typically lasting 10,000-20,000 miles. They are rarely used as OEM in modern vehicles due to their shorter lifespan and are not recommended for your Metris.

How to gap a spark plug

While many modern iridium spark plugs come pre-gapped from the factory, it's always a good practice to double-check the gap before installation. Incorrect gapping can lead to misfires, reduced fuel economy, and poor engine performance. For your 2019 Mercedes-Benz Metris with the 2.0L M274 engine, the recommended gap is 0.031 inches (0.8 mm).

To gap a spark plug, you'll need a wire-type spark plug gapping tool. Avoid using disc-style gapping tools on fine-wire iridium plugs, as they can damage the delicate electrode tip. Gently slide the appropriate wire gauge through the electrodes. If the gap is too small, carefully bend the ground electrode outwards slightly. If the gap is too wide, gently tap the ground electrode on a hard, non-marring surface to close the gap. Always be careful not to touch or bend the center electrode.

Replacement procedure tips

Replacing the spark plugs on your Mercedes-Benz Metris can be a DIY task for those with mechanical experience. However, always exercise caution and consult a repair manual if you're unsure.

• Coil-on-Plug Removal: The M274 engine uses a coil-on-plug ignition system. This means each spark plug has its own individual ignition coil mounted directly on top of it. To access the spark plugs, you'll need to carefully disconnect the electrical connector from each coil and then unbolt or unclip the coil to remove it. Be gentle with the connectors, as they can become brittle over time.
• Anti-Seize Debate: There is an ongoing debate about whether to use anti-seize compound on spark plug threads. Mercedes-Benz, along with many other manufacturers, often uses spark plugs with a special coating on the threads that acts as an anti-seize. Applying additional anti-seize can alter the torque specification, leading to over-tightening and potential cylinder head damage. It is generally recommended to follow the manufacturer's recommendation and not use anti-seize unless explicitly stated. Your OEM Mercedes-Benz plugs should have this coating.
• Dielectric Grease on Boots: Applying a small amount of dielectric grease inside the spark plug boot (the part that connects to the ignition coil) can help prevent moisture intrusion and make future removal easier. This grease is an insulator and won't impede electrical flow.
• Torque Specification: Always adhere to the specified torque setting for your spark plugs: 17 lb-ft (23 Nm). Over-tightening can damage the spark plug and the cylinder head threads, while under-tightening can lead to poor electrical contact and combustion gas leakage.

Known issues

The 2019 Mercedes-Benz Metris with the M274 engine generally does not have widespread, unique spark plug-related issues like some other manufacturers (e.g., Ford's two-piece spark plugs in the 3-valve Triton engines). However, like any engine, improper maintenance or using incorrect spark plugs can lead to problems such as misfires, reduced power, and decreased fuel efficiency.

Need plugs replaced? Find a shop on Repairius.