Would there be any advantage to running DOT 4/5 fluid in the clutch as well as the brake's if street driving is all my car sees??

 

You don't want to use DOT 5, It's Silicon based and reportedly collects pools of water, which rots your brake system from the inside out.

DOT 5.1 is compatable with DOT 3 or 4 braking systems.

 

I run a super DOT4 in my C6Z clutch hydraulics and would do the same if I were driving my C5Z still. I use Prestone DOT4 Synthetic (500F dry boiling point). It's $2.40 per 12 ounce can at Walmart.

Another good choice is GM-brand Super DOT4 [P/N 88958860], also with 500F dry boiling point. It has a slightly better wet boiling point but costs three times more than Prestone.

So I use the Prestone and change it often. Taking Care of Your Clutch

In your clutch you can also use serious racing brake fluid such as Motul. Much more expensive. And it still will fall prey to heat, but over a longer time.

Best fluid comparo I've found so far. Company does not sell brake fluid, but compiled the comparo as a service to its customers.

DOT3 in the brakes is fine for the street. Would suggest a full bleed of the brakes every 24-36 months.

Ranger

 

Seeing one of your post with your little bag full of the super DOT 4 and the syringe is what made me think of this issue. So I can mix the curent DOT 3 with the DOT 4? I guess since they are both a mixture of glycol and polyglycols it really wouldn't affect anything that much.

 

Realistically, it's useful to read the label on the can of DOT4 you plan to use. All the ones I've checked state they are compatible with DOT3.

Ranger

 

In real life mixing DOT3 and DOT4 can be done , just as you can mix dino ATF and synthetic ATF. Mind you its not recommended, and I have never heard of any short or long term effects. Ideally you would want to purge the system of the existing fluid before changing.
DOT 5 in not compatible, as others have said but DOT5 will not absorb mositure as does DOT3 and DOT4. I have used DOT 5 only when storing vehicles long term (10- 20 years) No moisture , no rust.
The real backdraw to DOT 5 is that it does not compress as well as DOT3 & 4. Your pedal will drop much lower before it becomes functional. Just feels weird.
Because DOT 4 has a higher temperature tolerance it works well for the C5 clutch and brakes.

 

I've been using a high quality DOT4 in both the brake and clutch systems - no complaints

 

Dave, What I've heard is that using DOT 5 for storage will lead to rotted out brake systems.

The problem is that moisture does get into the system, condensation, humidity, etc. And with the Silicon based DOT 5 it just pools up, and I think sinks. Where does it sink to? down into a low point in a steel brake line, which is now soaking in plain water. Since you don't drive your car much, it never boils the water out. The fluid never changes color so you don't see anything wrong, until the brakes quite working.

Now this could be something doesn't happen in AZ, or if your car is in a temp controlled garage. But I know it's happened around here.

YMMV

 

Avoid DOT 5 silicone fluids, as others have said. To switch to a DOT 5, you must clean the old DOT 3/4 fluid out completely. Mixing them can lead to problems. Also, if you track or autocross you car, be aware that DOT 5 silicone fluids can "gel" if they are overheated. Not a good thing in a brake system.

Stick with DOT 3/4, or a DOT 5.1. I've been using ATE Super Blue for many years, and have never had a brake problem associated with overheating the fluid. But I bleed my brakes fairly regularly anyway, between track events, so water absorbtion is not really an issue. But the stuff works great, and the ATE fluids, either Blue or Amber, are not expensive relative to the other racing fluids.

 

^^^ ATE Super Blue is a fine brake fluid. I'd suggest not running it in the clutch, though. The reason is that its color is so dark that it's hard to detect visually the build-up of particulate matter that is the tell-tale sign of impending clutch pedal issues. So, for the clutch, if your like ATE, suggest using the amber, not blue.

My suggestion is based on my personal experience trying ATE Super Blue in my 01Z clutch.

Ranger

 

QKSLRVZ;
My vehicles are stored in the SF Bay area with mild weather conditions. My experiences with DOT 5 have all been very positive. Example; I recently brought out of storage a 1979 Trans Am convertible w/11,000 miles that has been in wraps for 17 years. Its a WS6 w/ 4WD . The brake system was COMPLETELY purged of DOT3 (original) replaced w/ DOT 5. The system was topped off . The car is stored ( with others )in my insulated , but not temperature controled warehouse.
When the car was 'revived', again the brake system was disassembled
and purged of all DOT 5 before refilling with DOT4. No evidence was found of rust. The KEY to DOT 5 is the complete removal of DOT3 & 4. This requires disassembly and cleaning of calipers , MC, replacing rubber brake lines (if used),ect. One can not just drain the DOT 3 or 4 and refill with DOT5.
I have revived from long term storage a '85 Saleen Mustang and '87 Grand National, '87 Choo Choo El Camino with equal success in recent years. Moisture is not drawn into the system by the DOT5 , unlike the DOT3 & 4 brake fluids.
Disclaimer: as your conditions may differ , results may vary. hahahaha
All kidding aside , again the key is removing all trace of the original brake fluid from the system.
Thanks for the opportunity to clearify.
dD

 

I followed Rangers fluid advice using Prestone Dot 4 Synthetic. It's compatible with Dot 3 and has a higher boiling point, which is better for extreme conditions.

 

The frictional components in a braking system generate very significant amounts of heat, especially vehicles being operated in severe conditions like a police vehicle or service vehicle in mountainous regions. Vehicles used in operations such as these could have an increase of brake fluid temperatures of as much as 20%. This combination of higher heat and a reduced boiling point increase the possibility of fluid vaporization or vapor lock. Unlike brake fluid, vapors are highly compressible. When brake fluid becomes more compressible it loses its ability to transmit the necessary force to effectively stop an automobile. In the loss of brake force comes the loss of pedal response and conceivably, even loss of braking action. Vehicles equipped with Anti-lock Brake Systems (ABS) are much less likely to skid out of control, especially when the roadway is wet or slippery. The anti-lock system pumps the brakes automatically up to 15 times per second, thereby avoiding brake lock-up and skidding. The results are maximum braking and increased control. ABS systems, in some vehicles, send a sense of reduced resistance to the brake pedal.

Conventional DOT3 brake fluids will absorb and average of 2% or more of water in the first year of usage. In that period, the boiling point can drop from 401 degrees to 250 degrees, a reduction of over 150 Fahrenheit degrees.(6) Brake fluid designated a DOT4 possesses an important characteristic, having low moisture activity or improved ability to resist boiling point drop. This boiling point drop becomes essential in assuring safe brake operation.
With the resulting in the drop of the boiling points from the dry to the wet boiling point effectiveness, brake fluid should be changed at least annually. If the car is used in significant hard braking, then as often as possible.

In short, pick a brake fluid with the higher WET not DRY boiling points for harder and prolonged use.

On the Road race circuits we recommend picking a brake fluid with WET boiling points as close to if not above 400*


BRAKE FLUID COMPARISON CHART
Brand Wet Boiling Point Dry Boiling Point
Castrol SRF 518°F 590°F
Motul RBF600 420°F 593°F
Wilwood EXP 600 417°F 626°F
AP-600 410°F 572°F
ATE-Super Blue 392°F 536°F
Valvoline 333°F 513°F
Castrol LMA 311°F 446°F
Ford HD 290°F 550°F
Wilwood 570 284°F 570°F
PFC-Z rated 284°F 550°F
AP-550 284°F 550°F


Most of these brake fluids are difficult to find unless you mail order for them. For street use the Valvoline Super Synth or the Castrol LMA would be very good choices.

The ATE Super Blue ( also ATE Gold 600) and Motul may be found a Porsche or motorcycle dealerships.

I use the Castrol LMA in my wifes vette, my DD / tow vehical Pick up and as clutch fluid in all three of our vehicals. On the track car I use the Castrol SRF.

 

FLUID FACTS
To understand why moisture enters the brake system, you need to know something about the chemistry of brake fluid. Glycol-based DOT 3 and DOT 4 brake fluids are both "hygroscopic," which means they attract water. Leave a bottle of brake fluid open for several days and it will pull moisture out of the air like a magnet. This is one reason why vehicle manufacturers use glycol-based brake fluid: it disperses moisture that enters the system throughout the fluid to dilute the contamination. This prevents moisture from forming puddles in calipers or wheel cylinders that could boil and cause pedal fade if the brakes get too hot. The downside is that moisture lowers the boiling temperature of the fluid, increases its viscosity and promotes internal corrosion. That's why various chemical additives are put into the fluid to help it fight corrosion and oxidation.

All brake fluid must meet minimum performance standards established by the U.S. Department of Transportation (DOT). Most brake fluids usually surpass these standards, but it's important to know what the minimums are because of their potential impact on driving safety.

For all fluids that meet the DOT 3 specification, the minimum "dry" (contains no water) boiling temperature is 401° F and the minimum "wet" (saturated with water) boiling temperature is 284° F.

For all fluids that meet the DOT 4 specification, the minimum dry boiling temperature is 446° F and the wet boiling temperature is 311° F.


How do these numbers compare with most new brake fluids? For many years, Ford has used a special "high temperature" DOT 3 fluid with a dry boiling temperature of 580° F. General Motors, Chrysler and most "heavy-duty" aftermarket fluids typically have a dry boiling temperature of at least 475° F and some go as high as 550° F. By comparison, most DOT 4 fluids start out with a dry boiling temperature of 509° F or higher.

As you can see, most new fluids far surpass the minimum standards required by the DOT. This provides an extra margin of safety to minimize the risk of fluid boil and pedal fade in severe braking situations when the brakes get really hot. But, moisture contamination can quickly reduce the margin of safety.

According to some studies that have been done, brake fluid typically absorbs about one percent or more moisture per year of service life. Many two-year-old vehicles have as much as two to three percent water in the brake fluid. Imagine how much water must be in some vehicles that are six, eight or 10 years old and have never had the fluid changed!

As the fluid becomes contaminated with moisture, its boiling temperature drops. Only one percent moisture can lower the boiling point of some DOT 3 fluids down to 369° F. Two percent water can push the boiling point down to 320° F, and three percent can drag it all the way down to 293° F - which is getting dangerously close to the minimum DOT requirements.

Why don't the vehicle manufacturers simply switch to DOT 5 brake fluid that is silicone-based and repels moisture? One reason is that silicone brake fluid is very expensive compared to glycol-based fluids. Another is that silicone fluid contains more dissolved air and aerates more easily when pumped rapidly through small orifices that can increase pedal travel and reduce pedal firmness (a spongy pedal). Because of this, most vehicle manufacturers warn against using DOT 5 brake fluid in any vehicle equipped with ABS.

DOT 5 also cannot disperse moisture that enters the system throughout the fluid like DOT 3 and DOT 4 fluids. Any water that does get inside tends to "slug" and settle to the lowest point in the system, which is usually the calipers and wheel cylinders. Slugs of pure water are not something you want inside a brake system because they concentrate corrosion and increase the risk of pedal fade if the water gets hot enough to boil (it only takes 212° F to turn liquid water into steam).

Where DOT 5 fluid works best is in vehicles that sit for long periods of time (antique and classic vehicles that are stored during winter months or in a museum), or in vehicles that are operated in extremely wet environments (including off-road).

The best advice is to always follow the vehicle manufacturer's recommendations as to which type of brake fluid to use. For most vehicles, that's going to be DOT 3 or DOT 4 brake fluids.

 

Can DOT 5 Brake Fluid Be Used Instead of DOT 3 or 4?

Always refer to vehicle owner's manual for what the manufacturer recommends or warns against. As a rule, vehicles equipped with antilock brakes (ABS) should not use DOT 5 brake fluid.

DOT 5 brake fluid is silicone based. DOT 3 (standard) and DOT 4 (heavy-duty) are glycol-based. It can be distinguished from conventional brake fluids by its purple color (which comes from a dye).

Silicone does not absorb moisture. DOT 5 brake fluid does not become contaminated with moisture over time as conventional DOT 3 and 4 brake fluids do. Silicone is also chemically inert, nontoxic and won't damage paint like conventional brake fluid. It also has a higher boiling point.

Because of this, it is often marketed as a premium "lifetime" brake fluid. It is often used to preserve brake systems in antique vehicles and those that sit for long periods of time between use.

DOT 5 silicone brake fluid is also very expensive (costing four to five times as much as ordinary brake fluid), and it won't mix with glyco- based brake fluid (creating concern over sludging if all old fluid isn't removed when a system is refilled with silicone).

Silicone also has slightly different physical properties and compressibility, making it unsuitable for ABS systems calibrated to work with DOT 3 or 4 brake fluid.

 

No not DOT5 is an ABS brake system. DOT 5.1 can ( five point one)

DOT 5 when boiled foams and separates the water from the silicone fluid, and gets air into the fluid. causing the brakes to lock up the brake peddle with no braking force at all.