2023 Toyota Highlander — Spark Plug Type & Gap

Quick reference

Why the right plug matters

Choosing the correct spark plug for your 2023 Toyota Highlander is more critical than you might think. Spark plugs are not a "one-size-fits-all" component; each engine is designed to operate optimally with a specific plug type, heat range, and gap. Using the wrong plug can lead to a host of problems, including reduced fuel economy, engine misfires, rough idling, decreased power, and even accelerated engine wear.

Heat Range: This refers to the plug's ability to dissipate heat. A "hotter" plug retains more heat, while a "colder" plug dissipates it more quickly. The correct heat range ensures the plug tip stays hot enough to burn off carbon deposits but not so hot that it causes pre-ignition (where the fuel ignites before the spark). Toyota engineers have carefully selected the ideal heat range for your Highlander's engine, so sticking to the OEM specification or a direct equivalent is crucial.

Electrode Metal: Modern spark plugs utilize different metals for their electrodes, each with unique properties affecting durability and performance:

• Iridium: This is the most common and recommended material for late-model vehicles like the 2023 Highlander. Iridium is incredibly hard and has a very high melting point, allowing for very fine electrodes that create a more focused spark. This translates to longer service intervals (typically 100,000 miles or more) and improved ignition efficiency.
• Platinum: Platinum plugs offer good durability and a longer lifespan than copper, often lasting 60,000-80,000 miles. They are a step up from traditional copper but generally don't match the longevity or ultimate performance of iridium.
• Copper: While excellent conductors, copper electrodes are softer and wear much faster. They are typically found in older vehicles or high-performance applications where frequent changes are acceptable. Copper plugs are generally not recommended for your Highlander as they will not meet the factory-recommended service intervals.

How to gap a spark plug

Properly gapping a spark plug creates the ideal distance between the center and ground electrodes for the spark to jump. While many modern iridium plugs come "pre-gapped" from the factory, it's always a good practice to verify the gap, especially with aftermarket plugs, as shipping can sometimes cause slight changes. For your 2023 Toyota Highlander:

1. Obtain a gap gauge: A circular wire-style gap tool is generally preferred for iridium and platinum plugs as it's less likely to damage the delicate center electrode. Avoid using blade-style gauges that can scrape off the iridium or platinum coating.
2. Measure the gap: Carefully insert the appropriate wire gauge into the gap between the electrodes. It should slide in with a slight drag.
3. Adjust if necessary: If the gap is too small, use the bending tool on the gauge to slightly bend the ground electrode outwards. If the gap is too large, gently tap the ground electrode on a hard surface to close the gap. Never bend or apply pressure to the center electrode, as this can easily damage the plug.
4. Re-measure: Always re-measure after any adjustment to ensure accuracy.

Replacement procedure tips

Replacing spark plugs on your 2023 Toyota Highlander is a manageable DIY task for those with mechanical experience, but always consult your vehicle's service manual for specific, detailed instructions.

• Coil-on-plug removal: Your Highlander uses a coil-on-plug (COP) ignition system, meaning each spark plug has its own ignition coil directly mounted on top of it. To access the plugs, you'll need to carefully disconnect the electrical connector from each coil and then remove the coil hold-down bolt (if present) before pulling the coil straight up and off the spark plug.
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