Brake Fluid

[Shotgun]

I need to change my brake fluid.  The last time I did it (2 years ago) I used Valvoline Dot 3 & 4 synthetic.  I still have enough left to do it again.  My question is whether or not I can use fluid that has been sitting on the shelf for 2 years.  Otherwise, I can find Dot 3 fluid, and Dot 4 fluid, but not Dot 3 & 4 fluid.  Any suggestions?

[Ricky-D]

Honda specifies Dot-4.  It's cheap. Get a new can.

[Brad]

I need to change my brake fluid.  The last time I did it (2 years ago) I used Valvoline Dot 3 & 4 synthetic.  I still have enough left to do it again.  My question is whether or not I can use fluid that has been sitting on the shelf for 2 years.  Otherwise, I can find Dot 3 fluid, and Dot 4 fluid, but not Dot 3 & 4 fluid.  Any suggestions?

All the auto parts places here in Nevada stock the Valvoline Dot 3 & 4 synthetic, Wally World has it as well.  If what you have has been sealed tight so that it can not absorb moisture from the air it should be fine.

[BF]

Brake fluid is hygroscopic.  That means that it absorbs moisture from the air.  I wouldn't trust a two year old can of brake fluid that has been opened and had it's seal broken.  New brake fluid isn't that expensive. 

[Kingbee]

that the Dot 3/4 synthetic is NOT hydroscopic, which could also mean the change intervals could be longer, as moisture absorbtion is the reason for the 2 year interval.

Anybody know for sure?

[PatrickDoss]

On the one hand, if you kept the lid tight and kept the bottle in a relatively stable environment, I say use it.  On the other hand, it is relatively cheap stuff.

FYI: The only difference between DOT 3 & DOT 4 is the boiling point.  DOT 4 has a higher boiling point.  Otherwise, they're the same.  It's labeled DOT 3 & 4 for the folks who don't know that, but essentially, it's DOT 4.  DO NOT USE DOT 3 in the Valkyrie.  DOT 5 is another beast entirely, and also not to be used in DOT 3/4 systems.

As far as the synthetic not absorbing moisture, I'd probably stick with the assumption that it will, unless it specifically says otherwise on the bottle (I don't have one here to check out).

[Brad]

As far as the synthetic not absorbing moisture, I'd probably stick with the assumption that it will, unless it specifically says otherwise on the bottle (I don't have one here to check out).

Just read the bottle I have and dosen't say a word about it one way or the other

[Airetime]

I need to change my brake fluid.  The last time I did it (2 years ago) I used Valvoline Dot 3 & 4 synthetic.  I still have enough left to do it again.  My question is whether or not I can use fluid that has been sitting on the shelf for 2 years.  Otherwise, I can find Dot 3 fluid, and Dot 4 fluid, but not Dot 3 & 4 fluid.  Any suggestions?

Don't use the old stuff, get some new brake fluid.  Moisture builds up in your brake system at about 2% a year and it would be the same in an opened can.   

Fresh unopened Brake fluid has a higher boiling point than old previously opened fluid. As mentioned, Brake fluid is hygroscopic, so it absorbs moisture. The more moisture in the fluid, the lower the boiling point thus more brake fading. Since moisture promotes corrosion there is simply no reason not buy the new stuff and get rid of the old can. Trust me, you do not want to heat up the brakes coming down a hill or in traffic using old contaminated fluid, don't ask...

[Shotgun]

Why not?   Had to ask.

[Airetime]

Why not?   Had to ask.

OK, I knew someone would....

Wifes Blazer was used to commute to San Francisco years ago and I forgot to change the brake fluid out an it and it was probably 5 years old at the time. She was caught up in traffic and then braked going downhill. Yep you guessed it, no brakes, nada, zip, zero! She called me (to put it nicely) and I suggested that she get a cup of cofee at a nearby restuarant and let them cool for awhile (as well as she). She did, all ok, but the fluid was promptly changed . The one thing that is worse than "you" experiencing it? Your wife....... Don't forget!  Any questions?