A question from a member:

Originally Posted
would like your opinion on mixing DOT 4 and DOT 3 brake fluid.is this advisable? i plan on flushing the system as much as possible and not sure if i used DOT 4 last time but bought 3 this time.its been 3 or 4 years and i cant remember which i used...thanks.

Senor Honda answers......
If the DOT 3 is unopened, return it for a refund or get enough of DOT 3 to thoroughly flush the lines. If you think that DOT 4 is better and the DOT 3 cans are not opened, return them.
In either case thoroughly flush out the current fluid. Brake fluid is fairly cheap. If you get it from Walmart, it's even cheaper. If WM sells DOT 4, it must meet the federal DOT 4 standard whether it's the store brand or not

I never mix brake fluids. I thoroughly flush the lines. I follow the book as to which order the lines should be bled. When the master cylinder is almost dry, use a lint-free clean cloth and q-tips to thoroughly clean any dirt from the master cylinder bottom inside.

Clean the filter that is inside the master cylinder. I use brake cleaner from Walmart....lots cheaper than the name brands. I spray/clean the outside of the master cylinder especially around the plastic cap and the cylinder top.. Usually by the time I empty the second quart, there is only new fluid in the lines.

Reading the label is a pretty good guide.
Some MFG'ers may have compatibility within their own brand.
If the DOT 3 is old and you suspect it has been polluted by moisture, toss it out. Brakes are too important to take a chance.

I would get about two quarts of fluid plus about three small cans. Use the quart cans first. If you don't use all the small cans, take them back and get a refund if they are unopened. If they are opened, pour it all into the master cylinder and bleed it on out.
-Bob