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How Long Will My Iridium Spark Plugs Last?

November 8, 2011

A traditional iridium plug such as a Denso IK20 or NGK ZFR6FIX-11 both have iridium center electrodes, however the ground electrodes are a traditional nickel construction. The ground electrode will wear out first. Typically we have found you can expect 50-80k miles on an iridium plug.  But plug manufacturers have to temper their projections as driving conditions and motor modifications differ.  Additionally, because gradual wear will "round-off" firing points over time, the concentrated firing power and voltage requirement benefits will be reduced.  Therefore, NGK gives them a life expectancy of 40-50k miles and Denso assigns a recommended replacement interval of 30k miles.



Both Denso iridium racing plugs and some NGK iridium racing plugs have iridium center and a platinum ground electrodes. If installed in a regular engine, they would likely last longer than most people keep their car (barring any motor problems that can cause premature plug death). But, these usually come in heat ranges too cold for an unaltered motor and are usually used in racing applications where all bets are off.

For the traditional automotive market, the longest lasting plugs are the NGK Laser Iridium and Denso Long-Life Iridium series, which have iridium center and platinum tipped ground electrodes.  These OEM style plugs typically have special features designed for a specific engine and last 80-120k miles.


Ken Baginski

Mar. 2, 2016
Just replaced the original equipment Denso iridium spark plugs on my 2007 Honda Civic Si. Mileage 153,501! Was running fine. Now even better.

Allen B

Feb. 19, 2015
Have a 2006 Pontiac Grand Prix with factory iridium plugs and have nearly 130,000 miles on them. Getting ready to replace them as the car is starting to have a little misfire upon acceleration.

Danny Cifuentes

Oct. 8, 2013
My 2006 matrix comes with iridium plugs from factory ,recently i began to feel a little misfire when i accelerate ( 120.000 miles ) so i went to the auto parts and got ngks iridium i think they r the best !


Sep. 12, 2013
My 06 Hyundai Azera came with NGK. I have 99K miles on my car and so far haven't changed the plugs and the car's running just fine with good fuel economy. I have used a fuel system cleaner just twice in the life of the car. I intend to replace them at 125K miles. I do full synthetic oil change every 7K miles.


Jul. 31, 2013
My 2003 Toyota Matrix has over 380,000 miles and I only changed the Iridium plugs once at about 125,000 miles. The. current plugs have lasted for 250,000 miles. I add a bottle of STP fuel injector and sytem cleaner every 5000 miles to keep the fuel system clean.
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