Iridium Long Life Denso. Iridium Long Life plug is fast becoming the standard for today’s high-tech engines. Properties of DENSO’s patented Iridium alloy have broken through the spark plug technology barrier. Employing a revolutionary new 360° laser-welding process, DENSO has created a spark plug unlike anything on the market today. Engineered for long service life under the most extreme conditions, DENSO’s patented Iridium alloy is six times harder and eight times stronger than conventional Platinum and can handle temperatures in excess of 4,000°F. You’ll enjoy more horsepower, faster easier starts, less misfires under heavy loads, plus better conservation of fuel at all times! *By request/order.