View Full Version : synthetic brake fluid question

07-26-2011, 10:05 AM
DOT 3 Syn brk fluid
how would you go about changing over from regular brk fld?
run a bleed cycle to flush out the old using synthetic.

not sure if there are advantages w/syn or not i just have a couple big jugs of syn sitting around

any suggestions would be appreciated


07-26-2011, 10:34 AM
AFAIK synthetic and regular are compatible and may be mixed in the system, just as long as you stick to the same or better DOT approval levels. IOW, use only DOT4 with DOT4 or DOT4 into existing DOT3, etc. You would not damage anything if you put DOT3 into existing DOT4, although the system's boiling point would presumably go down. In an old Toyota truck it probably wouldn't matter, though.

The main thing is to NEVER, EVER, use DOT5 unless you really, really intend to.

DOT5.1 is OK with DOT3 and DOT4, but DOT5 mixed with anything other than DOT5 will make hydraulic fluid gum.

From the Valvoline product sheet: http://www.valvoline.com/pdf/Valvoline_Synthetic_DOT_3_&_4_Brake_Fluid.pdf

Valvoline's Synpower High Performance Brake Fluid is recommended for all ABS, drum or disc brake systems which specify either DOT 3 or DOT 4 brake fluid. Its premium low moisture formulation with a dry equilibrium reflux boiling point greater than 500F provides superior performance even under severe conditions. As brakes generate heat, brake fluid must remain liquid, without boiling to operate properly. Valvoline Synpower High Performance Brake Fluid is compatible with conventional brake fluid and meets SAE J1703, FMVSS No. 116 and DOT 4 specifications.

07-27-2011, 08:35 AM

Thanks :thumb: