brake fluid recommendations

TrackRat

Is there a concern about the age of brake fluid? I've got an unopened, sealed bottle of Motul thats been sitting on my shelf for I don't know how long. Was going to use it to flush my clutch but wanted to tap the expertise on here first to see if I'd be wasting my time with it.

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Rob Montgomery
'10 370Z Sport 6MT - Pretty much stock...
'88 Porsche 911 Turbo - You name it... its got it
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cossie1600

if you have an unlimited budget, sure why not.

i might be in the minority, but i like to save money where it makes sense. i wont spend money on rotoros and rims, but i will gladly spend it on tires, brake pads and synthetic oil

djpathfinder

If you read the label on most DOT4 fluids, it will tell you that you can mix DOT4 with DOT3. You might as well do it right the first time and flush your system with DOT4 brake fluid. If you're careful, you should be able to drain, flush and bleed with new DOT4 and use 2 quarts. Don't use DOT5...that is silicone based and is not compatible with ABS brakes. DOT4 is fine with ABS. DOT4 has a higher boiling point than DOT3, and therefore is more performance oriented. Likely overkill for most, especially if your car remains on the street 100% of the time, but if you want to splurge a little it doesn't hurt. Keep in mind, some luxury brands put DOT4 in their vehicles from the factory, eg. BMW, Mercedes-Benz.

In my opinion, if you can afford a good quality DOT4 go for it. If not, a "house brand" DOT4 is likely better than a DOT3 fluid.

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2010 370Z 40th Anniversary // SOLD

djpathfinder

Should be OK, if it is still sealed. If it is a previously opened bottle, you need to worry about exposure to dust, contaminants and moisture, all of which could lower the boiling point of the brake fluid...obviously not good.

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2012 GT-R Black Edition Jet Black
2010 370Z 40th Anniversary // SOLD

HKYStormFront

most performance shops recommend motul 600... it's not cheap but it's worth the price

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Mike

That is why they recommend it.

For 99.9% of drivers, the valvoline synthetic will be good enough.

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AP - Chris_B

Actually, the opposite is more likely true. The manufacturing process is the key to high-quality fluid. There are only a handful of chemical plants in the world equipped to make glycol ester-based brake fluid. Every label you see on the market comes from one of them. However, there are major differences in how the product is specified and what type of packaging process is used.

The better (more expensive) fluids on the market are packed in nitrogen, not air like some of the cheaper stuff. This means that the better fluids are actually "dry" when you crack the seal on the bottle. The cheaper fluids have already pulled whatever moisture they could out of the air they were packaged in, lower their boiling point efficacy. The cheap DOT4 stuff may have passed the SAE tests, but the product actually sitting on a store shelf may not have the exact same properties as what was tested in the lab.

Also, the more expensive fluids are typically more dense, meaning they have less dissolved air trapped in suspension. The more dense the fluid is (higher specific gravity), the better the brake pedal feels. Specifying a denser fluid adds production costs since it takes more times to make it. The cheaper fluids skip the extra steps.

But in all reality, if changing brake fluid every two years (like we are supposed to), the few extra bucks on a better fluid isn't really going to make much difference in overall maintenance costs per mile. Those tracking their cars will spend a lot more on fluid as they will replace it more often, but will also receive more benefit from the improved properties of the top shelf stuff (AP Racing PRF, Castrol SRF, Prospeed RS683, Motul RBF660 and a few others).

Chris

cossie1600

you should always compare the wet boiling point, not the dry since you should assume there is some type of moisture in the system or bottle already

ChrisSlicks

Valvoline synthetic was discontinued over a year ago.

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AP - Chris_B

If you plan on keeping brake fluid in the vehicle for over two years, then, yes, wet boiling points should be compared. Brake fluid, if made and stored correctly before use, absorbs about 1.5-2.0% moisture per year while in the vehicle. Most of this moisture comes through the OE rubber brake lines -- another argument for upgrading to stainless steel braided Teflon hose. It is also an argument against pressurized brake bleeders that don't have diaphragms.

Since the SAE WERBP (Wet Equilibrium Reflux Boiling Point) test measures wet boiling points at 3.5-4.5% typical moisture content (the reference fluid is at 3.70% +/-.05%), we should only be concerned with the wet boiling point if we stay with OE rubber lines, use cheap pressure bleeders and aren't that concerned with regular maintenance. If, as enthusiasts, we choose to keep up on maintenance and use better lines and bleeding methods, the dry boiling point is much more relevant to our use.

Chris

Mike

they just changed the bottle. The white bottle with blue label is still synthetic
Its 480/311 which is fine for the street


I'm all for quality stuff, but anything more is overkill on the street, assuming like AP Chris said, you are going to change your fluid every two years.

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NISSAN: 75 280Z / 86 300ZX GLL /87 Sentra SE / 03 350Z / 23 Z
Porsche: 93 968 / 23 Macan GTS / 93 968

cossie1600

you should anyway

NewYorkJon34

I just switched to a set of goodridge SS brake lines, & 4 bottles of Motul 600. The car is running great now.

Joehand1

So am I understanding that even though Nissan recommends DOT 3 that we should uses DOT 4 if we track?

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2009 370 Z
2006 Ford GT
1987 Porsche 911 Carrera

cossie1600

yes