Just about every dot 4 bottle I have seen says it is backward compatible with dot 3. May not be best for high performance racing applications but should be ok for regular street use.Since the system takes dot 3 I would say you will have contamination problems.
There is no "cycling" of fluid in the brake lines. There is no return line. You will get a little mix, but for the most part the old fluid will stay in the abs module unless cycled and bled.I only see some weird ball valves, no brake type turn and bleed on my abs module..I was going to worry, but what me? Just bled with racing super blu dot 4, cept the abs module which will probably cycle the old fluid with the reservoir when the abs activates in the future.. No?!
X2 for screw ! tried the motive power bleed rectangular plate with shop light hanger adjustment... Just a frickin mess everywhere..I use Super Blue and Super Gold brake fluid and alternate. Pour in gold and bleed until you see nice gold fluid coming out of the bleeder. I change fluid every two years (BMW & VW recommend interval) and then switch colors and bleed until new color comes out clean. I wish someone made a master cylinder reservoir retrofit with the screw cap top and then my pressure bleeder system would work in the burb.
Speed Bleeder are your friend:coolnana: