Dot 5.1 Degrading Once Opened?

Anonymous

So i Hear it degrades once opened! So, how long would it take to be rendered useless?
and I'm being forced to buy this
http://cgi.ebay.co.uk//Shell-Advance-Mo ... 12ffb87344

Because its the cheapest on the internet
do you think i will be able to get some cheaper?

Northwind

That's a good price, course it's about 10 times more than you need but you'd probably pay more for a smaller bottle... Most people say never to use an opened container, ie open it, use it, throw the rest away. I don't hold with that, it's horrible stuff so not good to throw away unneccesarily and I just find it wasteful, so I seal part-used bottles up firmly, date them, and store them somewhere as dry as possible. Been doing that for years and never had an issue. This of course doesn't mean you won't be killed.

Still, for pushbikes a 500ml bottle could last years and personally I wouldn't do that, but it'll end up being some arbitrary cutoff tbh.

M1llh0use

brake fluid = hygroscopic (absorbs moisture from air) the more moisture it absorbs the more it is likely to "boil" under heavy use this generating bubbles in the fluid.

unless you're using it regularly best to only use it from a sealed container.

bearing in mind that 5.1 was made mainly for racing where it would be changed at each meeting, so for motorycle use ~ 2-300 miles.

Northwind

Er, for general use you replace 5.1 on the exact same schedule as dot 4, it has better retention than dot 4 (ie, wets more slowly) so is actually less susceptible to loss of performance. Also starts from a higher dry boiling point- dot 5.1's boiling point when wet is barely higher than dot 3's when dry IIRC. Some race fluids are designed for very short lifespans but regular road-use 5.1 isn't.

nicklouse

if the container is sealed no problems.

Rockhopper

I've got a year old bottle (opened) of DOT 4 in my shed, I'd happily use it in my car,motorbike or mountain bike and not have the slightest worry.