which one is better, heard that iriduim isn't so good because it doesn't last long. also one of my friend has ngk iriduim and tune it today, made 155hp, wasn't so good anymore, so he install the v-power and gain more mid range power. v-power were new and iriduim were used?

 

In terms of plug function, the Iridiums are much more efficient and the best choice. As for longevity, the Iridium plugs actually don't wear out the Iridium center electrode. The ground electrode (the "L" shaped piece that you gap on traditional plugs) is made of nickel on the cheaper iridiums, which will wear out in 60-80K miles. Some of the higher-end NGK and DENSO iridiums have platinum ground electrodes, which will last much longer than your ownership of the car.

 

oh kewl, but that's werid, my friend had it dyno tune and the v-power made more midrange power.

 

The dyno tuner local to myself swears by the V powers over the Iridiums. He says just replace them more often.