Dear CFUs and otais,Recently my brake fluid warning light came on in the dash and long story short the culprit is the clutch master cylinder located somewhere behind the pedals and it has been leaking brake fluid when i park the car and had to top up the DOT4 fluid. Checked the maintenance history file and found out it has never been changed for 15yrs since 1995. So while at it i also change the clutch slave which is located outside beneath the engine on the right side.Now while at it, although it's not due until another 5000km i've decided to change all the beltings too. And i asked the mechanic to check the condition of all my pulleys, hydraulic & mechanical tensioners and the water pump. My mechanic said that tensioners are worn and one bearing had to be replaced immediately, but he also said that my main pulley is also due for change. I checked them myself too when the car was jacked up the ramp.He suggested for me that while i'm at it, why don't i change to the aftermarket pulleys which are lightweight high performance pulleys. I asked what material they're made of and he said aluminium. So my question to the CFUs here, does anyone know what is the pro & cons of using aluminium pulleys? Will it affect my stock engine in the long run? Is there any case of aluminium pulleys got blown in a bmw? Coz personally i would like to use original bmw germany ones coz it last very long like the current one, 15years!Of course logically the car will go faster due to the lightweight reciprocating pulleys but i'm more concerned with long term reliability...Thanks a lot guys and appreciate any inputs!