2017 Toyota Highlander Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2017 Toyota Highlander is more crucial than you might think. Spark plugs are not a universal component; they are specifically engineered for your engine's operating characteristics. The wrong plug can lead to reduced fuel economy, misfires, engine damage, and even catalytic converter failure.

Key factors to consider include heat range and electrode metal. The heat range refers to the plug's ability to dissipate heat. A "cold" plug dissipates heat quickly, ideal for high-performance engines, while a "hot" plug retains more heat, better for engines prone to fouling. Using a plug with an incorrect heat range can lead to pre-ignition (too hot) or fouling (too cold).

The electrode material also plays a significant role in longevity and performance. Most modern vehicles, like your Highlander, come with iridium spark plugs from the factory. Iridium is an extremely durable and hard metal, allowing for very fine electrodes that produce a strong, consistent spark for extended periods – typically 100,000 miles or more. Platinum plugs offer a good balance of performance and longevity, often lasting 60,000-80,000 miles. Copper plugs, while excellent conductors, have very soft electrodes and wear quickly, requiring replacement every 30,000 miles or less. While copper plugs might be cheaper upfront, the cost of more frequent replacement often outweighs any initial savings, especially considering the labor involved in accessing some engine locations.

How to gap a spark plug

Properly gapping your spark plug is essential for optimal engine performance. The 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 spark plugs come pre-gapped and generally shouldn't be adjusted due to their delicate fine-wire electrodes, it's always a good idea to verify the gap with a wire-type spark plug gauge.

To check the gap, gently slide the correct size wire gauge between the electrodes. It should have a slight drag. If adjustment is necessary (and only if the manufacturer explicitly states it's acceptable for the specific plug), use a gapping tool to lightly and carefully bend only the ground electrode. Never pry or bend the center electrode, as this can easily damage the iridium tip. For your 2017 Highlander, the recommended gap is 0.043 inches (1.1 mm).

Replacement procedure tips

Your 2017 Toyota Highlander utilizes a coil-on-plug (COP) ignition system, meaning each spark plug has its own individual ignition coil directly mounted on top. This setup eliminates spark plug wires, reducing resistance and improving ignition efficiency.

When replacing the spark plugs, start by carefully disconnecting the electrical connector from each ignition coil. Then, unbolt and gently pull the coil straight up to remove it from the spark plug well. Be careful not to damage the rubber boot on the bottom of the coil.

Anti-seize compound on spark plug threads is a topic of debate. While it can help prevent seizing in aluminum cylinder heads, many spark plug manufacturers advise against it, stating their plugs have a special coating that provides adequate anti-seize properties. If you do choose to use anti-seize, apply only a very thin layer to the threads, keeping it away from the electrode and taper seat, and reduce the torque spec by approximately 10-20% to avoid overtightening and potential damage to the cylinder head threads.

Before reinstalling the ignition coils, it's a good practice to apply a small amount of dielectric grease to the inside of the rubber boot at the bottom of the coil. This helps seal out moisture, prevents corrosion, and makes future removal easier.

The 3.5L V6 engine in some Highlander models has spark plugs located under the intake manifold, which requires additional disassembly. Be prepared for slightly more involved removal and reassembly for these cylinders.

Known issues

Fortunately, the 2017 Toyota Highlander engines (2.7L 1AR-FE I4 and 3.5L 2GR-FE V6) do not have widespread, well-documented spark plug-related issues like the Ford 3-valve 2-piece plug breakage or GM 5.3L ionization-sensing coil problems. Maintaining the correct spark plug type, gap, and torque, adhering to the recommended service intervals, and using quality replacement parts will ensure reliable ignition for many miles.

Need plugs replaced? Find a shop on Repairius.