Many brands are now labeled "synthetic fluid", and are different from the silicone fluids (dot5). Valvoline synthetic is Dot 3 & 4. and is very inexpensive and available almost anywhere. It seems to be less destructive to painted surfaces. Mercedes Factory, as usual, recommends that you use the Mercedes brake fluid from the dealer. The boiling point of brake fluid, becomes lower with age as it absorbs water. Water in your brake fluid will corrode the brake system on the inside. Water in your brake system can boil under hard braking and cause brake failure. Change every two years for best results.