OEM Brake Fluid Intervals vs. ATF Intervals

Joined
Aug 30, 2004
Messages
28,232
Location
CA
Most Japanese automakers are requiring brake fluid changes every 2-3 years and these vehicles are using DOT3. I have tested several vehicles with original DOT3 brake fluid after 10 years and moisture reads <2%. I do not see moisture intrusion being an issue on modern systems with DOT3 and have seen many vehicles get retired with the original brake fluid without issues.

On the other hand, transmission fluid changes are commonly lifetime fill with the exception of Honda.

Why are OEM's considering brake fluid services to be essential, but not transmission fluid? I have always considered brake fluid replacement to be a "nice to do" item, but hardly mandatory....especially since it can open a real can of worms for people living in the rust belt.
 
Joined
Nov 28, 2012
Messages
1,730
Location
Ontario, Canada
Most Japanese automakers are requiring brake fluid changes every 2-3 years and these vehicles are using DOT3. I have tested several vehicles with original DOT3 brake fluid after 10 years and moisture reads <2%. I do not see moisture intrusion being an issue on modern systems with DOT3 and have seen many vehicles get retired with the original brake fluid without issues.

On the other hand, transmission fluid changes are commonly lifetime fill with the exception of Honda.

Why are OEM's considering brake fluid services to be essential, but not transmission fluid? I have always considered brake fluid replacement to be a "nice to do" item, but hardly mandatory....especially since it can open a real can of worms for people living in the rust belt.
This is a "Guess" on my part, but it could be that with all the sensors in the braking system any amount of water above a certain % may cause problems by bringing rust into play. This % may be quite small, but as I said it's a guess. My MB required it every 2 years and my Lexus every 3.
 
Joined
Jun 8, 2016
Messages
2,691
Location
Texas, USA
I'm guessing mainly because all they need to do is get you through the warranty period, which modern automatics seem to do more easily than before on the original fill. 150,000 mi changes, or lifetime fill looks attractive to new buyers, even if it isn't in the best interest of the transmissions.
I'm sticking with 30,000 pan drops & filter replacement in the Texas climate. I'm trying to stick to 3 year brake fluid swaps, but I don't get alarmed if I go over that.
 
Joined
Jan 9, 2010
Messages
12,888
Location
Los Gatos, CA
I have no idea why our Lexus GS350 F Sport has "lifetime" ATF while Aisin, who made the transmission, recommends services.
Oh yeah, Lexus does not define "lifetime", so there's that...
By the way, after servicing brake fluid, I always get a better pedal. Placebo? Perhaps. Piece of mind? Absolutely.
 
Joined
Jan 26, 2012
Messages
924
Location
Omaha, NE USA
I'm thinking that the lifetime transmission fluid accomplishes two things: lower cost of maintenance for the first owner and it also discourages the quick lube places and DIYers from messing up the transmission by servicing it incorrectly.
 
Joined
Apr 25, 2017
Messages
7,968
Location
Ohio
Same thing with BMW and ZF.

BMW calls it "lifetime" while ZF recommends service
It goes back to "cost of ownership" - that is on BMW (in this example), not ZF. On the other hand, BMW is who has to provide the warranty coverage so you'd think they'd encourage maintenance that might help. Or maybe they can back-charge these cases to ZF (?).
 
Joined
Mar 8, 2012
Messages
16,352
Location
Colorado Springs
Most Japanese automakers are requiring brake fluid changes every 2-3 years and these vehicles are using DOT3. I have tested several vehicles with original DOT3 brake fluid after 10 years and moisture reads <2%. I do not see moisture intrusion being an issue on modern systems with DOT3 and have seen many vehicles get retired with the original brake fluid without issues.

On the other hand, transmission fluid changes are commonly lifetime fill with the exception of Honda.

Why are OEM's considering brake fluid services to be essential, but not transmission fluid? I have always considered brake fluid replacement to be a "nice to do" item, but hardly mandatory....especially since it can open a real can of worms for people living in the rust belt.
Bcs. moisture level in brake fluid is dependable on moisture level in environment. You have none where you live!
You still don’t know what is boiling point of 10yrs old fluid.
 

The Critic

Thread starter
Joined
Aug 30, 2004
Messages
28,232
Location
CA
It does. Average person rides brakes going downhill, doesn’t downshift. Here at some mountain passes in state and national parks we have forest rangers checking brake temperature in middle of descent.
Special use case. Not typical customer use.
 

The Critic

Thread starter
Joined
Aug 30, 2004
Messages
28,232
Location
CA
What about corrosion?
The fluid has corrosion inhibitors. The corrosion inhibitor package has never been a point of focus, though, I think a lot of corrosion issues require moisture to occur. With better-sealed systems, this is probably less of an issue than before.
 
Joined
Jun 3, 2002
Messages
8,974
Location
MI
It does. Average person rides brakes going downhill, doesn’t downshift. Here at some mountain passes in state and national parks we have forest rangers checking brake temperature in middle of descent.
You just criticized The Critic for comparing his low humidity conditions regarding moisture absorption of brake fluid, then turn around and use your mountainous brake use conditions to generalize how we flat landers use our brakes.
 
Joined
Mar 8, 2012
Messages
16,352
Location
Colorado Springs
You just criticized The Critic for comparing his low humidity conditions regarding moisture absorption of brake fluid, then turn around and use your mountainous brake use conditions to generalize how we flat landers use our brakes.
No, Critic doesn’t live in flat land as far as I know. By the way, flatlanders are the issue when they come to visit here, especially in winter.
Also, most flat land in US has MUCH higher moisture level in environment, so I wouldn’t bet that moisture level in brakes is same in CA and FL or MI.
 
Joined
May 7, 2004
Messages
12,749
Location
Nokesville, VA
The fluid has corrosion inhibitors. The corrosion inhibitor package has never been a point of focus, though, I think a lot of corrosion issues require moisture to occur. With better-sealed systems, this is probably less of an issue than before.

I think if the vehicle is old enough then you might develop a corrosion problem, especially here where it gets very humid in the summer.

I had an issue with the front brakes dragging on my 1998 Nissan Frontier about 3 years ago. It was then my dad's truck, he bought it used in 1999, and I found no record that the brake fluid had ever been replaced. So it most likely had 21-year-old brake fluid in it.

I replaced both front calipers, pads, and rotors, and brake hoses, and bled the brakes.

The fluid that came out looked quite bad. I'd never seen fluid quite that bad before.
 
Joined
Mar 8, 2012
Messages
16,352
Location
Colorado Springs
As The Critic said

You're using the unique situation of 1) tourists, 2) that live where it's relatively flat, 3) who come to visit Colorado, 4) in the winter, and 5) drive up and down mountain roads. 😂
Nope, people here do same thing (though flat landers are notorious). They ride brakes, as they do in CA and elsewhere. He said “average “ driver. Average driver is on love with brake pedal, regardless of location. Have you ever driven between LA and Las Vegas over passes?
This is ridiculous argument. It is like saying I don’t need to replace old tires bcs. I don’t drive fast. And we are talking bottle of brake fluid that can be purchased for $5 on Wal Mart and DIY in couple of hours.
 
Joined
Apr 25, 2017
Messages
7,968
Location
Ohio
This is ridiculous argument. It is like saying I don’t need to replace old tires bcs. I don’t drive fast. And we are talking bottle of brake fluid that can be purchased for $5 on Wal Mart and DIY in couple of hours.
Don't put words in my mouth or assume anything about me. I said nothing about what I do. I do brake fluid exchanges, own a Mityvac tool, and my preferred brake fluid is Pentosin LV.
 
Top