2016 Ram 3500 Spark Plug Specs & Replacement Guide

Quick reference

Why the right plug matters

Selecting the correct spark plug for your 2016 Ram 3500 is crucial for optimal engine performance, fuel efficiency, and longevity. The spark plug is responsible for igniting the air-fuel mixture in your engine's cylinders, and using the wrong type can lead to misfires, reduced power, and even engine damage.

Heat Range: Spark plugs are designed with a specific "heat range," which indicates their ability to dissipate heat. A plug that is too "cold" (dissipates heat quickly) can foul with deposits, while a plug that is too "hot" (dissipates heat slowly) can overheat and cause pre-ignition or knocking. Your Ram's engine is engineered for a specific heat range, and using the OEM-recommended plug ensures proper combustion.

Electrode Metal: The material of the spark plug electrode significantly impacts its lifespan and performance:

• Iridium: This is the most common and recommended material for modern engines like those in your 2016 Ram 3500. Iridium plugs offer superior durability and a finer electrode tip, leading to a more consistent and powerful spark. They typically have a longer service life, often extending to 100,000 miles.
• Platinum: Platinum plugs are a step up from copper, offering better corrosion resistance and a longer lifespan than copper. They are often rated for 60,000-80,000 miles.
• Copper: Copper plugs have a large electrode and provide excellent conductivity. However, they wear out much faster and are generally not recommended for modern engines that specify iridium or platinum, as their shorter lifespan would necessitate more frequent replacements than the engine's design anticipates.

How to gap a spark plug

While many iridium and platinum spark plugs come "pre-gapped" from the factory, it's always a good practice to verify the gap before installation. Even a slight variation can impact combustion efficiency. You'll need a spark plug gap tool, typically a wire-style or coin-style gauge.

1. Check the gap: Carefully insert the appropriate feeler gauge wire or coin into the gap between the center and ground electrodes. It should slide in with a slight drag.
2. Adjust if necessary: If the gap is too small, use the bending tool on the gauge (or a dedicated gapping tool) to gently pry the ground electrode outward. If the gap is too large, carefully tap the ground electrode on a hard, flat surface to slightly close the gap. Never bend the center electrode, especially on iridium or platinum plugs, as this can damage the fine tip.
3. Re-check: Verify the gap again to ensure it matches the specification.

Replacement procedure tips

Replacing spark plugs on your 2016 Ram 3500 involves working with a coil-on-plug (COP) ignition system.

1. Access: Depending on your engine (5.7L or 6.4L HEMI), access to all spark plugs can be challenging, particularly those towards the rear of the engine bay. You may need to remove air intake components or other obstructions for better access.
2. Coil-on-Plug Removal: Each spark plug has an individual ignition coil mounted directly on top of it. Carefully disconnect the electrical connector by depressing the release tab and pulling. Then, gently twist and pull the coil pack straight up to remove it. Avoid prying against other components, as this can damage the coil or surrounding parts.
3. Anti-Seize Debate: Historically, anti-seize compound was commonly applied to spark plug threads. However, with modern spark plugs that often feature specialized coatings and aluminum cylinder heads, many manufacturers, including Mopar for the HEMI engines, recommend against using anti-seize. The concern is that anti-seize can act as an insulator, altering the torque value and potentially leading to over-tightening and plug damage or stripping of the cylinder head threads. Always consult your service manual, but for most modern Ram HEMI engines, it's best not to use anti-seize.
4. Dielectric Grease on Boots: A small amount of dielectric grease applied to the inside of the spark plug boot (the rubber part that connects the coil to the plug) can help prevent moisture intrusion, facilitate easier removal in the future, and ensure a good electrical connection. Be sparing with the grease, as excessive amounts can attract dirt.
5. Torque is Key: Tightening spark plugs to the correct torque specification is critical. Over-tightening can strip cylinder head threads or damage the spark plug, while under-tightening can lead to leaks, misfires, or the plug backing out. Use a good quality torque wrench.

Known issues

Fortunately, the 2016 Ram 3500 with either the 5.7L or 6.4L HEMI engine does not suffer from the notorious spark plug issues seen in some other Ford or GM applications (like the Ford 3-valve two-piece spark plug breakage). The Mopar (NGK/Denso equivalent) plugs specified for these engines are generally robust and reliable when replaced at the recommended intervals using the correct procedures.

However, it's important to ensure you're using genuine or high-quality aftermarket iridium plugs as recommended. Using incorrect platinum or copper plugs could lead to premature wear and misfires.

Need plugs replaced? Find a shop on Repairius.