Wow! Very impressive to see how clean they are after that amount of miles. Before I read your post having just looked at the pic, I thought they were new! I also use the best possible fuel that we can get here in Australia which is 98 RON, (BP Ultimate) and use Motul synthetic oil, changed every 5000Km (twice as often as Nissan recommends) along with a quality K&N oil filter. I also have an oil cooler and a large capacity sump. I hope my valves are in similar condition too.
