Brake Fluid Comparison

I would use any brand name DOT3 since it is a standard.

 

Ask Luscious Garage on their Facebook page. They advised me against it at 30,000, even though my car was in their shop on the rack.

 

I've used Valvoline synthetic brake fluid on my other cars for years. Supposedly less hygroscopic than regular fluid.

 

Mike, don't go by the highest boiling point alone, some high boiling point fluids absorb water faster than some lower boiling point fluids. Unfortunately, that data is hard to find.

Unless you are doing track many days in your car or fording deep streams I don't think it's very likely that you will benefit by changing your brake fluid yet. Try some test strips and see what they tell you.

 

I had the dealer flush my brake fluid at 30,000 miles. Cost was $129.08. I typically have the brake fluid flushed, or do it myself, every two years or 30,000 miles. I always notice an improvement in braking and consider it cheap insurance to prevent costly brake component repairs. Prius brake components are even more expensive than those on conventional cars.

I don't think it matters so much which brand of fluid you use as long as it is a major brand and hasn't been sitting on the shelf for months. I have used Valvoline and Prestone DOT4 synthetic fluids with excellent results.

I am more interested in your methodology:

• Which flush method and tools are you planning to use, i.e. power flush, vacuum pump, pump brake pedal? In my opinion, power flush is best; vacuum is OK, but can be tedious; and, pumping the brake pedal can get you into trouble.
• Do you have a scan tool to excercise the ABS?
• If you don't have a scan tool, how do you plan to disable the hybrid brake system?
• Anything else you plan to do due to the special aspects of the hybrid brake system?

I am not asking these questions to quiz you or question your capabilities. I hope this goes well for you and you can educate us on how to do it. I have been considering doing it myself on my Prius but have not because I am not sure of how to safely deal with the hybrid apsects.

 

If the system says to use DOT 3 -- that is what I would use. DOT 4 does needs to be changed out at two years .... You can get specialized fluids in all the classes -- that can often overlap in spec.

Why introduce a fluid into a system that will never come into play and introduces the potential for more moisture.

 

You can just refresh the fluid by sucking it out of the reservoir and addind fresh fluid. This way you don't have to break the bleeders open and throw codes. This is much more than the average owner does.

 

You have it backwards. DOT4 is an improved version of DOT3. DOT4 can be used in any system which calls for DOT3 because they are both glycol based. DOT4 is preferable to DOT3 because it has a higher boiling point and is less hydroscopic (absorbs less moisture) than DOT3. The below link provides a good comparison between DOT3 and DOT4. It also describes silicone based DOT5 which should not be used in a Prius, and DOT5.1 which is a higher performance glycol based fluid.

Brake Fluid Grades

What does "never come into play" mean? If you mean you don't think brake fluid needs to be flushed, that is certainly your choice. Since I keep my cars a long time, I find is more cost effective to do lower cost preventive maintenance now than high cost repairs later.

Flushing does NOT "introduce(s) the potential for more moisture". To the contrary, flushing the old contaminated brake fluid out of the sytem and replacing it with new brake fluid removes moisture.

 

Sounds like you have everything covered, the key items being the Toyota Techstream Lite software and interface cable. Can you give some more information on your Techstream hardware and software.

• What kind of device is the software on (scanner, PC, etc.)?
• If someone wanted to buy the same hardware and software as you are using, how much would it cost and where would one purchase it?

Thanks.

 

Den 49: DOT4 does indeed have a minimum boiling point that is higher then the minimum for DOT3 -- but you can get fluids that are DOT3 that have higher boiling points than the minimum and are higher than DOT4. On a performance car that will regularly need the higher boiling point the higher spec in needed. DOT4 is more resistant to moisture absorption up to a point - it is then actually more susceptible to moisture intrusion -- so it must be change out or you will get more corrosion with the 4 then the 3 -- that is why you don't see change intervals for the 3 on many makes.

The 4 will also give you better feel on systems that are set up for the use the 4 as the 3 will possibly have more moisture and lower boiling point. The Prius does not need the 4 as it has no "feel" and no performance .... and you don't want the potential of more moisture with a possible extended interval. So ........use the 3 .. the 4 gains you nothing. The above is simplified a bit.

 

VW specifies Super DOT4 for their cars. All the rest I've owned used DOT3. That's what I use.

 

Modern brake systems require very little maintenance. Years ago pad material did not last as long, rotors required more maintenance and the various seals did not perform to the level of todays products. Since the brake system is "closed" -- moisture could only enter during maintenance procedures or seal/ hose degradation ..... all now greatly reduced. I can't tell you the last time we had a moisture issue in any of our DOT3 cars. We always beed out the fluid when we do any brake work on the DOT3 cars. On the DOT4's you have to change out the fluid every two to three years. The main problem is down at the calipers - moisture can cause rust ...some guys only squirt the first few ounces. Since the fluid tank is clear and most cars contain enough fluid in the tank for the whole pad wear -- we leave them alone. You are not gaining much by replacing the fluid in an always closed tank. Always use a new can of fluid when adding. I just had this done on our MB Wagon .......since no pad work in the near future -- less than $100.00. Most american cars have DOT3 and no change interval .....

 

Honda uses DOT3, and recommend to change the fluid every 3 years. They also recommend to not mix fluid brands. The latter might be overkill, but probably safest to follow, ie: stick with the same brand.

Further edit: revised "change" to "mix" (underlined). Still, amounts to the same thing: unless you could completely purge the current fluid, if you switch brands you will be mixing.

 

My understanding is that the Prius callipers Are aluminium and the pistons are plastic to reduce weight, this also must go some way towards reducing corrosion.

The boiling point of the fluid is mute in the Prius since the brakes with regen rarely get warm with friction braking born out by the longevity of the life disc pads. More moisture is let into the brake system through people taking the filler cap of for no good reason (this also lets in dust) than by any other means.