If want to change to Bosch Super 4, iridium spark plugs or whatever, as long as diff from stock spark plugs, if really want to see the diff, the plug cable also have to change first, change to a bigger one. Then you can see slight fuel save on this. If the plug cable never change, the fire is more or less the same.
Another thing is when buying athis types of spark plugs, must always go to spare parts shops. There will be much cheaper. Like the Boch Super 4, I can get it around rm60 if not mistaken(my last plug change), now the price all shooting sky high. Like Castrol Magnetic now selling for rm67, my last service was 3 months ago only cost rm63.
Forgot to ask, A Bosch Super can last around 50000km without changing it. So my last change was 2years back, maybe is almost time for me to change it. Will update the price ASAP. Maybe the price now is rm80...