Denso Iridium IKH27 Spark Plug Specifications Whatever your use or engine set-up the correct choice of spark plug is very important. Iridium is very heavy and dense metal ensuring that Denso spark plugs have a longer lifespan than OEM ones withstanding more than 100.000 km in standard use. Which heat range to choose ? If the letters (for example IKH) indicate the spark plug's shape and thread size the numbers (from 20 to 27) indicate the heat range basically meaning how well the spark plug can operate in intense conditions. The higher the number the more the spark plug will be cold and more adapted to tuned engines and sporty use. A cold spark plug is designed to operate at higher than average temperatures and disperse the heat inside the cylinders improving combustion performances and engine reliability reducing the risk of detonation. However make sure you only fit cold spark plugs if your car requires them otherwise you could encounter problems such as difficult cold starts and rough idling. Also do not install cold spark plugs if your engine runs on E85 fuel. In short : IKH20 : standard grade for stock engines or for use with E85 ethanol IKH22 : one grade colder than standard for lightly tuned or sporty engines used both on the road or the track IKH24 : two grades colder than standard for tuned and powerful engines used mainly on the track IKH27 : three grades colder than standard for high power and heavily modified engines used in intense conditions Application List Non-exhaustive list. Audi RS3 BMW 1-Series E8X : 125i 130i (N52) BMW 3-Series E9X : 325i 330i (N52) BMW 5-Series E6X : 523i 525i (N52) BMW 6-Series E6X : 630i (N52) BMW 5-Series F07 F10 F11 : 523i 528i (N52) BMW X1 E84 : 2.5i 2.8i (N52) BMW X3 E83 : 2.5i 2.8i (N52) BMW X3 F25 : 2.8i (N52) BMW X5 E70 : 3.0i (N52) BMW Z4 E85 & E86 : 2.5i 3.0i (N52) Cadillac CTS V6 Daihatsu Sirion Ford Focus RS 2.5L Duratec (JZDA) Ford Focus ST (HYDA) Honda Civic EP 1.3i & 1.4i Honda Insight 1.0i ECA1 Infiniti FX35 (VQ35DE) Infiniti FX45 (VK45DE) Kia Carnival II Kia Magentis II Kia Sorento II Lexus LS460 (1UZ-FE 3UZ-FE) Lexus RX350 Lotus Evora Mercedes Classe E S21 (03-09) E55 AMG Mercedes Classe E W21 (02-08) E55 AMG Mercedes Classe E C215 (99-06) CL55 AMG Mercedes CLS C21 (04-10) 55 AMG Mercedes SL R230 (01-12) 55 AMG Mitsubishi Colt Z30 Mitsubishi Eclipse 2.4 (4G69) Mitsubishi Outlander CU Nissan 350Z 280 & 300 bhp (VQ35DE) Nissan Almera 1.8i Nissan Micra K12 Nissan Pathfinder R51M Nissan Primera 1.8i Nissan X-Trail Nissan SR20VE & SR20VET engines Opel Signum V6 Opel Vectra V6 Peugeot 206 S16 & RC Peugeot 307 1.6i 16V Peugeot 405 MI-16 (87-93) (XU9J4Z) Peugeot 406 V6 Peugeot 407 V6 Porsche 997 after 2008 Porsche Boxster after 2009 Porsche Cayenne after 2010 Porsche Panamera Renault Clio V6 (L7X) Renault Espace IV V6 Renault Laguna V6 Renault Velsatis V6 Smart Forfour Brabus Subaru Forester after 2005 (EJ20 EJ22 EJ25) Subaru Impreza after 2005 (EJ20 EJ22 EJ25) Subaru Legacy after 2005 (EJ20 EJ22 EJ25) Suzuki Swift Sport ZC32 (M16A)