which is the best of the 2? also is it a case of totally removing all the old stuff before refilling?

This was asked the other day. Lots of facts and figures posted up.

No you don't want to drain the system, getting air in is bad news. A flush with a couple of litres will be ample.

I used about a litre

Doesnt really matter either or as it will be better than oem stuff

After bleeding mine the old fluid was black in colour absolutely fubar

Hello you usually tend to find that performance DOT 4 fluid has got the same (or very close to) temp rating as the DOT5.1

As mentioned above about a 1ltr bleeding the system will do the trick - do not drain as that will take you about 5times longer trying to get the air out of the system!

AwesomeMike

cheers for the quick replys. so which is best then either or??

it all depends on the boiling points given on the back of the bottle. Look for Dry and wet boiling points and possibly chose the best wet boiling point.

Here is the other thread that was mentioned above. Which is the best brand DOT 5.1 brake fluid?

From memory, the Racing DOT 4 stuff has a very good dry boiling point, but not so good wet - I think I remember having a good look at the bottles whilst I worked at Halfords at uni. It's designed to be very good fluid, but only used for a short period of time. If I remember correctly, I believe it suggested changing the fluid after every track day/race day, to keep the brakes at their optimum. I'm not sure what it would be like on day to day use though.

yeah your right i read that. it said change after each track day

For a road car I would use Castrol Response dot 4, good for a couple off years hard driving and well proven. If tracking it I would be using ATE racing blue or other racing fluids and would be changing it more often.