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How Long Will My Iridium Spark Plugs Last?

January 24, 2017

Traditional Single Iridium Plugs  Denso's Iridium Power and NGK's Iridium IX series have iridium fine-wire center electrodes with tranditional nickel ground electrodes.  The ground electrode will wear out first.  Typically we have found you can expect 50-80k miles on a traditional 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.

OE Iridium Long Life Plugs   NGK Laser Iridium and Denso Long-Life Iridium plugs feature an iridium tipped fine wire center electrode, and platinum tipped ground electrode.  Bosch Double Iridium includes places iridium in the ground electrode inlay as well.  These OEM style plugs typically have special features designed for a specific engine and last 80-120k miles.

Aftermarket Long Life Iridium Plugs Autolite Iridium XP, Champion Iridium, Bosch Iridium and Denso Iridium TT bring the features of OEM Iridium long life plugs to the market, with an iridium or iridium enhanced fine wire center electrode and platinum or iridium/platinum tipped ground electrode. Under normal operating conditions, expect a good 100k miles out of these plugs.

Iridium Racing Plugs  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.


John R

Feb. 18, 2018
My 2006 Avalon has the original OEM ridium spark plugs and they have 407,000 miles on them. The engine doesn't miss at all and it still gets the same MPG as it did when new... amazing. I did look at them around 200,000 and the front 3 on the v6 looked good so I didn't replace them. Now, 407,000 and going strong..

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.
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