Originally Posted by garcmol
Because there isn't a separate resevoir. It shares the brake fluid resevoir.
Yes you want a separate clutch fluid reservoir. you don't want contaminants in the brake system.
And if you drive a standard transmission, the clutch fluid picks up a whole lot of clutch particle dust from the slave cylander. The fluid needs to be changed out occasionally.
I used to use a baby's snot sucker - looks like this, to suck up the old fluid and then add fresh fluid in the clutch reservoir.