Q: What brake fluid should I use? A: Mitsubishi specify DOT 3 or 4 brake fluid however only use DOT 4 and DOT 5.1, do not use fluid lower than DOT 4, in fact you will probably have a hard job finding DOT 3 fluids about nowadays. Use a glycol-ether based brake fluid but it is worth noting that these fluids are hygroscopic (absorb moisture). Water absorbing into the fluid leads to a drop in the fluid boiling point and therefore brake fade can occur, it can also lead to corrosion of the caliper pistons if not changed regularily. It has been found that moisture absorption is mainly by diffusion through the brake hoses, the fluid at the Master Cylinder may be fine but it can be a different story at the calipers! That is why it is recommended for general road use the brake fluid should be changed at a very minimum of once a year. For the best performance, change the fluid every six months although some fluids do last longer than others. DOT 5 fluids are Silicone based and are not recommended for high performance use. Although Silicone fluids are not hygroscopic they are highly compressible and offer inferior lubrication. Any water that does get in the system is not absorbed in the fluid but sits in little pockets boiling and forming vapour bubbles at over 100°C and freezing into ice crystals below 0°C leading to poor braking performance compared to glycol-ether based fluids. The trapped water can also cause bad pockets of corrosion. DOT 5.1 is a different story though and these are non-silicone fluids that pass the DOT 5 specification. 'Super' DOT 4 and DOT 5.1 fluids are generally superior to the standard DOT 4 fluids as they are treated with Boric acid which partially esterifies the free OH (hydroxyl) groups making them capable of reacting with water to help nullify it's effects. These fluids should last longer than similar specified DOT 4 fluids. Silicone-ester based fluids are a completely different story to normal Silicone fluids. Patented by Castrol they are virtually the perfect fluid offering brilliant performance and an excellent viscosity however, they are quite hygroscopic and expensive to buy. General notes on Brake Fluid Hygroscopic brake fluids can absorb moisture through plastic containers, that's why the better fluids come in metal containers. It's not a problem having a plastic container but remember to only buy enough fluid for what you need and only use fluid from freshly opened containers. Never use Mineral based fluids, they require braking systems specifically designed for their use. When working out the quality of brake fluids you generally need to know two things: Dry boiling point This is the temperature at which vapour bubbles may start to form in the fluid. Wet Boiling point This is the temperature at which vapour bubbles may start to form in the fluid subsequent to moisture absorption under specified conditions (approx. 3.5%). The higher the two figures the better, pay attention to the wet boiling point. Low figures mean you may need to change the fluid fairly regularly or performance will drop. Athough not generally stated, it is also worth noting the Cold Viscosity rating especially for use with ABS systems. The thinner the viscosity of the fluid the better the flow rate through the ABS micro valves. Fluids are classified a certain DOT rating depending on their performance: Reference Standard for testing: FMVSS 116 Requirements DOT 3 DOT 4 DOT 5 Dry boiling point min. °C 205 230 260 Wet boiling point min. °C 140 155 180 Cold viscosity at -40°C mm²/s 1500 1800 900 Wet boiling point = after 3.5% moisture absorption         Some of the more popular brake fluids used by Lancer owners and their specifications: Brake Fluid Dry boiling point min. °C Wet boiling point min. °C Street price per litre (approx.) Castrol SRF 310°C 270°C £40 Motul RBF 600 312°C 216°C £13 AP 600 300°C 210°C £20 ATE 'Super Blue' 280°C 200°C £16 Castrol Response 'Super DOT 4' 280°C 190°C £9 AP Ultra 5.1 270°C 186°C £8 AP 550/1 287°C 140°C £10               Back to question page