What is the difference between DOT 3 and Dot 4.

Its all about the boiling point. Dot 4 higher.

What does your car call for

Roy

You can add dot 4 to a dot 3 system, but you can't add dot 3 to a dot 4 system.

Dot 4 is pretty standard and should be easily found at auto parts places or vw dealers.

You shouldn't have to add fluid to your reservoir. The only time the fluid should be low, is
if the brake pads have worn down or if there is a leak.

Have your brakes checked.

Thomas