Brake Fluid: DOT4 or DOT3?

[MR22ZZ]

So DOT 5.1 isn't silicone based?
I've always wanted to try DOT 5, purely for the non paint peeling properties. Although I imagine it would have a longer service life as it's also not hydroscopic.
Is changing to 5 just a matter of performing a really good flush?

just remember that DOT 5 and DOT 5.1 are not the same thing.

As with TooF, I've used Motul RBF600 after switching from Castrol Super DOT4 both of which are great products but the Motul gives better feel in harsher conditions as you would expect from it's higher max temp, but thanks to Psychofox I've turned to Penrite Sin 600 brake fluid (~$17.50 from your local Repco) which for not much more than the Castrol Super DOT4 has similar properties to the Motul. In a cost vs effectiveness scale, it's my far the front runner, in my mind at least.

[TooF]

wow the penrite is $17 a bottle. i thought it was cheaper then that. in that case makes a good argument for the motul. last one i got was only $25.

[MR22ZZ]

There are lower grades from Penrite for cheaper.

[TooF]

yea but i havent gone putting in 800deg pads in to go put rubbish fluid behind them

i knew psychofox mentioned a penrite one that was up to spec as the motul and i just had in my mind for some reason that it was quite cheap. admittedly i dont know what the retail price of the motul is, like i said i only paid $25 for my last bottle.

[MR22ZZ]

You must also remember that Penrite is an Australian company with low marketing costs and overheads, where as Motul have a relatively high marketing budget, especially in motorsport and Motorcycle racing, and this is reflected in the price... not to mention brand awareness and value... which I see suckered you in...

I think there are a couple of tests performed side by side by memory, I'll see if I can find the results again.

[Talasas]

Thanks for info guys but I really was just interested to know why Toyota insist on DOT3 even now. I'm not interested in using DOT5 or 5.1 because of their properties. This is just my plain old road car and I wanted to know if there are any drawbacks (such as 4agte suggested with seals) in using DOT4 or if I should stick with the DOT3 Toyota recommend.

[oldcorollas]

after X amount of time, DOT4 and DOT3 will have same boling points anyway since they absorb water even sitting on the shelf....

if you look at the MSDS or data sheets for dot3/4 many of them seem to have the same compounds in them, just in different % to get the different properties.

edit: is dot4 more hy?roscopic than dot3?
\/\/ fucker

[YLD-16L]

Brake fluid is hygroscopic not hydroscopic

[BigWorm]

Brake fluid is hygroscopic not hydroscopic

Piss off wanker! (I was the first person in this thread to get that wrong, so I'll take that correction as aimed half at me).

As for why Toyota still insist on using DOT 3, when did they last insist on this? Toyota aren't likely to issue a servicing update to all owners of a 20+ year old car advising them to change to a better brake fluid, when their original recommendation is still available & going to work as intended.

[rick q]

The other thing to be wary of with DOT5 (silicon based) is that is holds microscopic air bubbles - leading to a slightly spongy pedal. And because it doesn't absorb water, any water in the brake circuit will find its way to low points - offering a perfect beginning for corrosion.

It's expensive (Harley shops seem to be one of the few places you can buy it) at about $25 / 250ml.

Getting rid of it is also a pain. You need to replace EVERY rubber seal in the braking system and be careful to fully flush all traces from the lines. DOT5 mixed with other brake fluids turns into a jelly - not good.

Changing from DOT5 to DOT4 in mine has resulted in a much firmer pedal as well.

[oldcorollas]

As for why Toyota still insist on using DOT 3, when did they last insist on this? Toyota aren't likely to issue a servicing update to all owners of a 20+ year old car advising them to change to a better brake fluid, when their original recommendation is still available & going to work as intended.

as of 2000, they were still recommending DOT3.

the only "toyota" branded fluid you can buy from shops is DOT3... i can't remember what the honda and nissan ones were... one of them may have been DOT4..

but seriously tho, the difference in a street car is negligible... far more important is how often you change it, to keep the fluid "non-waterised"
when new, if you are boiling brake fluid on the street... you have a problem with your driving style.

[WDE_BDY]

as mentioned above, dot 5 is purely a race fluid,

DOT 5 is purely a SHOW fluid, not a race fluid. Its only benefit is not fucking your paint. If used on a race car you still get moisture in your brakes due to heat cycling (a lot more than a road car) but it isn't absorbed. So instead of being absorbed and reducing the boiling point of your fluid to 300 degrees, it forms pockets and boils at 100 degreees.

Not good.

Callum

[Moppitt]

DOT 5 is purely a SHOW fluid, not a race fluid. Its only benefit is not fucking your paint. If used on a race car you still get moisture in your brakes due to heat cycling (a lot more than a road car) but it isn't absorbed. So instead of being absorbed and reducing the boiling point of your fluid to 300 degrees, it forms pockets and boils at 100 degreees.

Not good.

Callum

I was told by a former ap racing employee (engineer or mechanic...not sure) that is its also good for military vehicles as they can sit in stockpile for years and then be returned to service in the minimum amount of time. A non hy..roscopic fluid will also help to reduce the maintenance costs while in storage.

Also I suspect that brake pedal feel is less of a concern in military vehicles than it is in our enthusiasts cars.

[Gavatron]

The Toyota Genuine stuff we use at work is still DOT3. All the brand new cars come with DOT3 in them too.

I just use the Toyota stuff in my cars, mainly cos it's free I probably change my brake fluid more often than anyone else for that same reason