I thought DOT4 meant a certain boiling temp. Each company has different boiling temps.
a minimum wet boiling temp must be met to be labeled a certain DOT. for street use always use the highest wet boiling temp, this allows replacement interval to be extended past every 2 yrs.
road racers want the highest dry boiling point.
DOT 5.1 even though a higher WBT is designed for ABS systems and has a different viscosity than DOT 4. Some state braking performance can be reduced using 5.1 in a 4 or 3 system.
All DOT 3 and 4 fluids are synthetic and have been for decades don't believe the marketing hype.
DOT 5 is the silicone based fluid and is strictly a race track item and cannot be mixed with the other DOTs.
