Brake fluid should be flushed every 2 years because it is hydroscopic. Absorbed water causes corrosion but it also reduces the fluid boiling point. Once the fluid/water boils the gas is compressible which causes temporary a loss of braking. Small amounts of gas in the system can be from leaky nitrogen accumultors, whatever the source, any gas the system causes a spongy pedal. Flushing wth firm up the pedal.
All but the very old vehicles will use Mercedes Benz Dot 4 fluid. Dot 3 can be replaced with Dot 4 by pressure flushing the system. We use Super Dot 4 which is backward compatible and used on new vehicles. SBC vehicles need to be flushed with a specified sequence when replacing the hydraulic unit and to properly bleed the system. This requires a laptop and a pressure flush machine with variable pressure. Without these it may not be done properly. Please contact us if you have questions or need this type of work completed. Generally, using anything but the approved brake fluid from a sealed container could cause extensive damage to your braking system..
Call us if you need to schedule a brake or brake flush service.