As brake fluid gradually absorbs moisture over a period of time which reduces the boiling point, you may not notice the difference during normal use. In a heavy use situation - long down hill, high speed emergency braking etc. the fluid can boil due to the heat build up and once that happens you have vapour in the system rather than fluid. This means no brakes and a brown trouser moment.!!

Brake fluid isn't that expensive and on most bikes it's an easy job to bleed the new fluid through the system. I personally change mine every two years as I've witnessed the effects of vapour lock (as its known...). Better to be safe than sorry.

That's my tuppence worth ;-)

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