high sages- want to put some brake fluid in my 92 245 for the first time . ive always used dot 3 synthetic clear fluid in my american tanks. have to put some fluid in since i think i took out too much to avoid an overflow when i pushed back the caliper pistons in a rear wheel brake pad replacement . brakes work fine , except the brake failure light is on. figure it is the low fluid switch in the brake revevoir. the fluid is green in the masters resevoir. heres the issue; the bentley manual says to only use dot 4 type fluid. is the dot 3 synthetic ok or should i get a can of dot 4 when i add some. thanks tons oldduke