2018 Mercedes-Benz Sprinter Spark Plug Type, Gap & Torque

When discussing the 2018 Mercedes-Benz Sprinter, it is important to note that the vast majority of these workhorses on the road are equipped with diesel engines (the 2.1L and 3.0L), which utilize glow plugs rather than spark plugs. However, for fleet operators and drivers utilizing the gasoline variants (such as the 2.0L M274 Turbo I4 that became available in this generation of Sprinters), spark plug maintenance is a critical part of keeping your van on the road.

As an ASE-certified master technician, I can tell you that ignoring spark plug service on a heavy-duty, turbocharged European application is a quick ticket to misfires, reduced fuel economy, and expensive catalytic converter damage. Here is your comprehensive guide to the spark plug specifications, gaps, and torque requirements for the gasoline-powered 2018 Mercedes-Benz Sprinter.

Quick reference

(Note: If you have a 2.1L or 3.0L BlueTEC diesel Sprinter, your vehicle uses glow plugs, not spark plugs. Glow plug service intervals and procedures are entirely different.)

Why the right plug matters

Modern turbocharged engines like the Mercedes 2.0L operate under immense cylinder pressures and high temperatures. Selecting the right spark plug is not just a suggestion; it is vital for engine survival.

Electrode Metal: Mercedes-Benz specifies Iridium spark plugs for this application. Iridium is significantly harder and more durable than platinum or traditional copper. The fine-wire iridium center electrode allows for a concentrated spark that easily bridges the gap even under high boost pressures, preventing blowout. Never downgrade to a copper or platinum plug in this engine—it will severely degrade performance and fail prematurely.

Heat Range: The heat range dictates how fast the spark plug pulls heat away from its tip and transfers it to the cylinder head. Using a plug that runs too hot can lead to pre-ignition and catastrophic engine knock, while a plug that runs too cold will quickly foul with carbon during long idle periods (common in delivery vans). Always stick to the exact heat range specified by the OEM NGK equivalent.

How to gap a spark plug

While most premium iridium plugs (like the NGK SILZKFR8E7S) come pre-gapped from the factory at 0.028 inches (0.7 mm), it is always best practice to verify the gap before installation. Shipping and handling can sometimes result in a bumped plug that closes the gap.

1. Use the right tool: For fine-wire iridium plugs, never use a traditional coin-style gapper, as you risk snapping the delicate iridium tip. Use a precise wire-type feeler gauge.
2. Measuring: Gently slide the 0.028" wire between the center and ground electrode. It should slide through with a slight "drag."
3. Adjusting: If the gap is too tight, use the bending notch on your gap tool to gently pry the ground electrode up. Never pry against the fragile center iridium tip. Make slight, careful bends until the correct measurement is achieved.

Replacement procedure tips

Replacing plugs on the Sprinter’s 2.0L engine involves a standard Coil-on-Plug (COP) architecture, but because it is a Mercedes, a few specific procedures apply:

• Accessing the Coils: You will need to remove the engine cover and carefully disconnect the electrical connectors to the ignition coils. The plastic locking tabs can become brittle from under-hood heat; press them gently and do not force them.
• Removing the Coils: Pull the ignition coils straight up. If they are stuck, a slight twist while pulling can help break the seal on the rubber boot.
• The Anti-Seize Debate: Mercedes-Benz (and NGK) generally advise against using anti-seize compound on the spark plug threads. The aftermarket NGK plugs feature a special trivalent metal plating that prevents seizing in the aluminum cylinder head. Adding anti-seize acts as a lubricant and can easily cause you to over-torque the plug, stripping the threads in the head.
• Dielectric Grease: Always apply a very small dab of dielectric grease to the inside tip of the coil boot before reinstallation. This prevents moisture intrusion, stops high-voltage tracking, and ensures the boot won't stick to the new plug during the next service.
• Torque is Critical: Use a calibrated torque wrench and tighten the plugs to precisely 17 lb-ft (23 Nm). Over-tightening can distort the plug or strip the aluminum head, while under-tightening can lead to the plug backing out and causing severe cylinder head damage.

Known issues

While the Sprinter 2.0L does not suffer from the catastrophic two-piece spark plug breakage seen in early Ford 3-valve engines or the widespread ionization-sensing coil failures of some GM trucks, it does have a few quirks to watch out for.

The primary issue on the M274 engine architecture is coil pack wear and oil intrusion. The spark plug tube seals in the valve cover can sometimes leak as they age. Before removing your old spark plugs, shine a flashlight down the tube. If you see oil pooling around the base of the spark plug, you must replace the valve cover gasket and tube seals. Pulling the plug while oil is pooled will allow that oil to drain directly into the combustion chamber.

Additionally, because fleet Sprinters often endure high idle times, carbon tracking on the porcelain insulator is common if the replacement interval of 45,000 miles is ignored. Stick to the schedule to keep your fleet running smoothly.

Need plugs replaced? Find a shop on Repairius.