DOT 3 and 4 are compatible with each other- - - -the DOT 4 just has a higher boiling point. That's useful if you have disc brakes and tow trailers, etc. Either one can be used for light to medium duty applications.
Jerry

"It is better to be silent and be thought a fool than to speak and eliminate all doubt!" - Abraham Lincoln
Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
There is nothing noble in being superior to your fellow man; true nobility is being superior to your former self. - Ernest Hemingway
Love your enemies and drive 'em nuts!