As above i accidentally topped up my brake fluid with dot 3, ment to use dot 4. It was only about 200ml of fluid.
Ive heard dot 4 is ok in dot 3 systems, but what about viseversa.
Should be ok, right. its only different boilings points isnt it. and ill get it flushed before the dot 3 will have a chance to get to the calipers.

Should be fine. Dot 4 is just the improved Dot 3. Then after that you have Dot 5.1 (not Dot 5 as that is a significantly different fluid and not intercompatible). Dot 3, 4 and 5.1 should mix fine, but it's not ideal to use an inferior fluid.
My recomendation would be to dispose of what ever remaining Dot 3 you have in order to prevent that ever happening again (I'm assuming you've only got a half used bottle or something and not a 20L drum of the stuff). Dot 4 is compatible in Dot 3 applications and it is an improved fluid.

yea its molike a quarter bottle, it was from my prelude, i just saw it in the boot of the lude and went, oh i need fluid.
Then read it after and was like oh noes.
But thanks for that.

if it was an opened bottle sitting in the boot the fluids probably stuffed anyway..

the two fluids should mix fine, as they're both made from the same stuff, its just the dot 4 has a higher temperature rating ..