Longest life brake fluid for vehicle destined to get little maintenance.....

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Aug 27, 2005
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My 2011 Prius is headed a long long way away with my daughter and I doubt she will ever flush the brake fluid. I have tested the fluid yearly for moisture and its always been dry, but now, with the vehicle setting sail and probably will not be driven home again, I am planning a brake fluid flush.

I snagged 4 liters of ATE sl.6 about 5 years ago, then chickened out using it in a 2005 Forester (overkill). Its been sitting on a dry shelf, inside the metal cans and plastic bags from ATE. You think its OK?

I'm not sure its the best choice anyhow for a Prius. I just want the VERY LONGEST LIVED brake fluid. Which probably means the one that is least hygroscopic / water absorbing. Prius brakes are pretty low maint. First set of brake pads made it to 120k miles.

Prestone Max DOT3 says 100,000 mile change interval. Its listed as synthetic, whatever that means.
Prestone Max DOT4 says only 75,000 miles.

What are some other, better choices? Again, for longevity. Not performance.
 
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My 2011 Prius is headed a long long way away with my daughter and I doubt she will ever flush the brake fluid. I have tested the fluid yearly for moisture and its always been dry, but now, with the vehicle setting sail and probably will not be driven home again, I am planning a brake fluid flush.

I snagged 4 liters of ATE sl.6 about 5 years ago, then chickened out using it in a 2005 Forester (overkill). Its been sitting on a dry shelf, inside the metal cans and plastic bags from ATE. You think its OK?

I'm not sure its the best choice anyhow for a Prius. I just want the VERY LONGEST LIVED brake fluid. Which probably means the one that is least hygroscopic / water absorbing. Prius brakes are pretty low maint. First set of brake pads made it to 120k miles.

Prestone Max DOT3 says 100,000 mile change interval. Its listed as synthetic, whatever that means.
Prestone Max DOT4 says only 75,000 miles.

What are some other, better choices? Again, for longevity. Not performance.
I'd not use that ATE just to be sure, your life rides on brakes performance.
As far as I know DOT 3 is less hygroscopic than DOT 4, but has a lower boiling point, so better for humidity, but not
as good in heavy breaking.
 
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All brake fluid is synthetic. Most people treat brake fluid as a lifetime fluid. Go to any 'buy here pay here' lot and try to find anything without black brake fluid. I would use OEM for this reason. Maybe Motorcraft (ford oem) for a higher boiling point.
 
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IMO Unless your daughter is driving the Prius at 120 mph every day, I don't think it needs fancy brake fluid.
 
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IMO Unless your daughter is driving the Prius at 120 mph every day, I don't think it needs fancy brake fluid.
I, too, have a daughter who is mechanically ignorant; and I don't care what the car needs. I want the best fluids that money and technology can come up with for her car. It is an act of love. It's my daughter. To the OP: I have a high degree of respect for "The Critic's" advice.
What is in my daughter's master cylinder is Bosch Esi6. https://www.boschautoparts.com/p/esi-brake-fluid
 
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As others have said above, DOT3 is better for long-term use as it resists water contamination better than DOT4.
DOT4 has a higher boil point so it is better for high performance if you flush/change it every year.
Most cars can take either DOT3 or DOT4, your choice.
 
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That pretty much what I said. I want long life. Not fancy.
Looks like you answer yourself in your first post. (y)
Generally, DOT 3 is longer life than DOT 4, that is in your first post, 100K vs 75K.
I would guess that 100K should last at least 4 years for your daughter which hopefully is the length of college.
 
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That pretty much what I said. I want long life. Not fancy.
120mph is irrelevant.
Going downhill 40mph and riding brakes is what is an issue.
DOT3 is OK for Prius. Based on my experience with Land Cruiser Prado and Sienna, Toyota brake components are mediocre. Going DOT4 might create issues and in my case I cannot point whether master cylinder in my Sienna failed bcs. DOT4 or just bad quality. But if I kept Sienna, I would stick to DOT3.
Keep in mind that Toyota doesn’t have brake fluid interval while it has fir Lexus vehicles! So, whether Toyota doesn’t like its drivers as much as Lexus drivers, I don’t know, but I would change it every 3 years as it is not only moisture but copper levels etc.
 

cdherman

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Bosch ESI6 is intriguing. Looks like a rebadged ATE product. Maybe I already have 4 liters of it??!!

Couple votes for the Prestone MAX DOT 3 here and elsewhere.

Dealer wants $180 plus tax, which would right at $200. No thanks.
 

cdherman

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Looks like you answer yourself in your first post. (y)
Generally, DOT 3 is longer life than DOT 4, that is in your first post, 100K vs 75K.
I would guess that 100K should last at least 4 years for your daughter which hopefully is the length of college.
Actually, a little more ahead of college, but good guess:) Finished medical school and starting residency. Needs a reliable vehicle and Dad will be a long ways away. Actually pretty responsible kid, but it always made Dad feel good to dote over her vehicle. By the time she's done with residency and fellowship (5-7 years) it will be in its last years and certainly not worth a 1000 mile drive to bring home. But even a nearly 20 year old Prius might have resale value at that point, if its still running. 50mpg sure is nice these days.....
 
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I would never use DOT4 in any vehicle that will not see 2-3 year fluid changes.
nobody changes dot4 either and it still generally outlives the rest of the vehicle, shrek green bottle and all.

any 10 year old car with dot 3 will fail out copper test strips. change at reasonable 5 year intervals and move on with life.
 
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nobody changes dot4 either and it still generally outlives the rest of the vehicle, shrek green bottle and all.

any 10 year old car with dot 3 will fail out copper test strips. change at reasonable 5 year intervals and move on with life.
My Honda odyssey 2006 never had its dot3 brake fluid changed, I changed it a couple months ago. It does last quite a while, but I would never stretch it....15/16 years. It was quite black though.
 
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Do what you can within reason and move on. Help her understand the importance of maintaining a car and if she chooses not to, then she can learn the cost of it. We all want what's best for our kids but they have to learn the value of repairs and maintenance for themselves or all the doting we do will be for not and lead to hard feelings.. Either from us (parents) or them.. Or both.
 
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Just make sure you are properly tooled to perform a brake fluid flush on Toyota hybrids. The process is a bit different than a conventional system. If you do not have a scan tool that is capable of initiating the air bleed function, things can get weird.
 
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Here is a web page that lists over a hundred brake fluids. If you sort by the "Wet Boil" column, you'll find which ones are the best/worst when the fluid inevitably absorbs water.


The best ones are for racing, where brake & fluid temperatures get ludicrously high, and the top one is Castrol React SRF: about $70-$80 a liter...yow!

I recommend teaching your daughter that all liquids are incompressible so any cheap old brake fluid works...as long as it doesn't boil. That means don't ride the brakes when going down long hills--a good habit no matter what. (This may not even happen; don't Priuses have regenerative braking?) As a medical student she'll have a good appreciation for how systems work, what the failure mechanisms are, and how to prevent them. Best wishes.
 
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