Sold in complete sets (includes all spark plugs for your engine).
NGK's Iridium spark plugs help your Audi S4 achieve optimal performance. Iridium is the biggest breakthrough in spark plug technology since platinum. We offer a full selection of the 3 most popular performance iridium plugs NGK offers: Laser Iridium, Iridium IX, and Iridium Racing.
NGK Laser Iridium:
NGK Laser Iridium plugs offer incredible precision and OE quality. The fine wire tip provides a stable and strong electrical arc to ignite the air/fuel mixture consistently, reducing misfires and hesitation. Most NGK Laser Iridium spark plugs also use a platinum ground electrode. This provides slower wear, superior anti-fouling, and improved overall performance. Most applications are only available in the stock heat range for this plug type.
NGK Iridium IX:
NGK Iridium IX plugs provide strong and continuous performance, even under the most severe situations. These plugs are designed for the performance enthusiast looking to get the most out of their build. Most applications have multiple heat ranges available.
NGK Iridium Racing:
Iridium Racing spark plugs are a specialized plug designed to withstand the harshest engine conditions and provide excellent throttle response. They feature a copper core, triple seals, and a special insulator for superb heat extraction. Most applications have multiple heat ranges available.
NGK Iridium Spark Plugs Key Features:
- Iridium conducts electricity better than platinum, and is 6 times harder and 8 times stronger than platinum.
- Highly durable and resistant to fouling.
- Ultra-fine 0.6mm diameter iridium center electrode provides superior ignition performance.
- The trivalent metal used for the threads gives superior anti-corrosive and anti-seizing properties, making it easy to replace if anti-seize compound was not used during installation.
- Requires fewer volts to fire than any other plug.
Heat Range Notes: For most vehicles, for every 100 hp you add to your engine, you may go to the next colder step plug. This rule does not directly apply to newer vehicles with coil-on-plug setups (consult your tuner or email us for details).
Gapping Notes: These plugs come pre-gapped and usually do not need to be re-gapped. Even with small variations in the factory set gap, the ultra-efficient firing power design of these plugs will compensate for those small variations. If you do decide to gap the plugs, NEVER use a round gapping tool to check or change the gap, and
never let any piece of metal touch the iridium center electrode or porcelain. Instead, carefully use needle nose pliers or a special spark plug gapping tool (that doesn't touch the center electrode) to bend the ground strap to the desired height, then re-check the gap with a calibrated gapping tool.
