Will 1.5L be enough for a complete brake fluid exchange?

For most vehicles, yes — 1.5L covers a full system bleed without leftovers. Check your service manual for reservoir capacity if you're running a larger system or multiple bleeding points.

Can I mix this with my existing brake fluid?

You can, but a full flush is always the safer call. Old fluid picks up moisture and contaminants over time. If you're doing a partial top-off in an emergency, compatibility between DOT grades matters — stick to the same spec your vehicle calls for.

Do I need any special tools or equipment to do this flush?

You'll need a brake bleeding kit (one-person or two-person, depending on your preference), clear tubing, a catch bottle, and basic hand tools. The fluid itself is straightforward — the labor is in the bleeding process, not the product.