2021 Mercedes-Benz Sprinter Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2021 Mercedes-Benz Sprinter is crucial for optimal engine performance, fuel efficiency, and longevity. The spark plug ignites the air-fuel mixture in your engine's combustion chambers, and an unsuitable plug can lead to misfires, reduced power, increased emissions, and even engine damage. Key factors to consider are the heat range and the electrode material.

Heat Range: Spark plugs are designed with a specific heat range, which refers to their ability to dissipate heat. A "hot" plug retains more heat, while a "cold" plug dissipates heat more quickly. Using a plug that is too hot can lead to pre-ignition and detonation, causing engine damage. A plug that is too cold can lead to fouling, negatively impacting performance. Mercedes-Benz engineers have carefully selected the appropriate heat range for your Sprinter's engine, so sticking to OEM or equivalent aftermarket plugs is vital.

Electrode Metal: Different materials are used for the spark plug electrodes, each with its own advantages:

• Iridium: This is the most common material for modern, long-life spark plugs, including those in the gasoline Sprinter. Iridium is extremely hard and offers excellent durability, allowing for a very fine electrode tip. This results in a stronger, more consistent spark and extended service intervals.
• Platinum: Platinum plugs offer good durability and performance, often found in OE applications that require longer service intervals than copper. They offer a good balance of performance and cost.
• Copper: While copper is an excellent conductor of electricity, it is softer and wears down more quickly. Copper plugs typically have a larger electrode and require more frequent replacement. They are generally not found in modern Mercedes-Benz vehicles due to their shorter lifespan.

For the 2.0L M274 gasoline engine, the OEM plugs are iridium, designed for extended life and consistent performance.

How to gap a spark plug

Spark plug gapping ensures the correct distance between the center and ground electrodes, which is essential for a strong, consistent spark. While many modern iridium spark plugs come pre-gapped from the factory and should generally not be adjusted, it's always good practice to verify the gap, especially with aftermarket options. For the 2.0L M274 gasoline engine, the recommended gap is 0.031-0.035 inches (0.8-0.9 mm).

To gap a spark plug, you will need a spark plug gapping tool, commonly a wire-type or coin-style tool.

1. Check the gap: Carefully slide the appropriate wire gauge or the edge of the coin-style tool between the center and ground electrodes. It should slide through with a slight drag.
2. Adjust if necessary: If the gap is too small, use the gapping tool to gently bend the ground electrode outwards. If the gap is too wide, carefully tap the ground electrode on a hard, non-marring surface to bend it inwards. Make very small adjustments at a time.
3. Re-check: Always re-check the gap after any adjustment to ensure it falls within the specified range.

Important Note: For iridium plugs, be extremely careful if you need to adjust the gap. The fine iridium tip can be easily damaged. It's often recommended to avoid gapping iridium plugs unless absolutely necessary and to use a wire-style gapping tool if you must.

Replacement procedure tips

The 2.0L M274 gasoline engine in your Sprinter utilizes a coil-on-plug ignition system, meaning each spark plug has its own ignition coil directly mounted above it. This design eliminates traditional spark plug wires and improves ignition performance.

Here are some tips for replacing spark plugs on your 2021 Sprinter:

1. Gather tools: You'll need a spark plug socket (typically 14mm for these plugs), a ratchet, extensions, a torque wrench, dielectric grease, and potentially a coil pack puller.
2. Access the coils: The ignition coils are usually located on top of the valve cover, beneath a plastic engine cover. Carefully remove any covers or wiring harnesses that obstruct access to the coils.
3. Disconnect and remove coils: Disconnect the electrical connector from each coil. Then, carefully pull the coil straight up and off the spark plug. A gentle twist might help. Be careful not to damage the coil or the electrical connector.
4. Remove spark plugs: Using your spark plug socket and extension, carefully unscrew each spark plug. Turn counter-clockwise. Once loose, you can often remove them by hand or with a magnetic spark plug socket.
5. Inspect old plugs: Examine the old spark plugs for signs of wear, fouling, or other issues. This can provide insight into your engine's health.
6. Apply anti-seize (Debate): The use of anti-seize on spark plug threads is a common debate. Most modern spark plugs, especially those with nickel-plated shells (like the OEM plugs for your Sprinter), do not require anti-seize. In fact, applying anti-seize can act as a lubricant and lead to over-torquing, potentially damaging the cylinder head threads or the spark plug itself. If anti-seize is used, reduce the torque value by approximately 10-20% as per some manufacturers' recommendations. However, for Mercedes-Benz applications, it's generally recommended not to use anti-seize if the spark plug body is nickel-plated.
7. Install new plugs: Carefully thread the new spark plugs into the cylinder head by hand to avoid cross-threading. Once finger-tight, use a torque wrench to tighten them to the specified torque: 15.5 lb-ft / 21 Nm. Adhering to the correct torque spec is crucial to prevent damage to the spark plug or cylinder head.
8. Apply dielectric grease: Apply a small amount of dielectric grease inside the spark plug boot (the part of the coil that sits on the plug). This helps to seal out moisture and improve electrical contact. Do not get dielectric grease on the actual electrode.
9. Reinstall coils and covers: Push the ignition coils firmly back onto the spark plugs until they seat properly. Reconnect the electrical connectors and reinstall any engine covers or harnesses.

Known issues (Diesel Glow Plugs)

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