The iridium tipped OEM spark plugs of a 3rd generation (2011, 2012, 2013 & 2014) Kia Optima with the Theta II 2.4 liter GDI inline four cylinder engine should last up to 100,000 miles. But they should be checked several times before reaching that mileage to verify that the motor is working properly and to prevent them from becoming stuck or “frozen” in the engine.
Kia Optima 2.4L I4 Engine Spark Plugs Replacement Guide
