Break fluid question

[ellupo11]

Anybody have an idea why Honda used DOT 3 brake fluid vs. DOT 4? I don't think I've seen the 3 on any newer cars... my '89 CRX takes DOT 3. Just seems a bit weird to use 3 on a performance car

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[apl360]

Moisture absorption is supposed to be slower with dot3. I think that’s the only advantage it has over dot4

I haven’t had my car long. I had no idea it was dot3 instead of 4. Pretty surprising

 

[Amm5890]

I assumed they used atleast the Honda brand dot 4 stuff. Only reason I would think is because they knew anyone tracking their car would switch it out regardless to something like motul/castrol/endless rbf. Does it confirm that the factory fill is dot 3 ?

 

[apl360]

I assumed they used atleast the Honda brand dot 4 stuff. Only reason I would think is because they knew anyone tracking their car would switch it out regardless to something like motul/castrol/endless rbf. Does it confirm that the factory fill is dot 3 ?

I just googled. It said the fl5 uses LV dot4. But google be lying so I dunno

 

[ellupo11]

Moisture absorption is supposed to be slower with dot3. I think that’s the only advantage it has over dot4

I haven’t had my car long. I had no idea it was dot3 instead of 4. Pretty surprising

Just had mine for 5 weeks. Was looking through the manual when I saw it. Just seemed strange.
Yes it has slower absorption rate but also lower boiling point

 

[AZCWTypeR]

I'm not tracking, so I prefer DOT3. Over the years, I've never had issues with DOT3 (unlike DOT4). I keep cars for 10+ years and motorcycles for much longer.
I've seen algae and gelling as DOT4 gets older. Both are bad IMO. I generally exchange brake fluid about every 3 years, but sometimes life gets in the way.

 

[ellupo11]

I assumed they used atleast the Honda brand dot 4 stuff. Only reason I would think is because they knew anyone tracking their car would switch it out regardless to something like motul/castrol/endless rbf. Does it confirm that the factory fill is dot 3 ?

 

[apl360]

I'm not tracking, so I prefer DOT3. Over the years, I've never had issues with DOT3 (unlike DOT4). I keep cars for 10+ years and motorcycles for much longer.
I've seen algae and gelling as DOT4 gets older. Both are bad IMO. I generally exchange brake fluid about every 3 years, but sometimes life gets in the way.

You can’t go 3 years unless U also replace the reservoir cap for a new one bro….. other wise U gotta flush every two years

been using both dot3 and 4 for a long time and always swapped at 2 years with zero issues.

 

[Spart]

To answer OP's question, I think Honda uses DOT3 in everything. So kind of like there being one oil filter to stock, they have one type of brake fluid to stock.

If you track the car, swap it for the DOT4 of your choice. Can't go wrong with Castrol SRF.

I just googled. It said the fl5 uses LV dot4. But google be lying so I dunno

Google AI search results are wrong more often than not. It's such a joke.

 

[ellupo11]

To answer OP's question, I think Honda uses DOT3 in everything. So kind of like there being one oil filter to stock, they have one type of brake fluid to stock.

If you track the car, swap it for the DOT4 of your choice. Can't go wrong with Castrol SRF.



Google AI search results are wrong more often than not. It's such a joke.

But Honda does sell DOT 4 fluid.
Just seems weird to go with a 3

 

[Spart]

But Honda does sell DOT 4 fluid.
Just seems weird to go with a 3

Yes, they also have a specific oil filter for the S2000.

But the rest of the lineup uses the standard oil filter and DOT 3, and that makes sense logistically to stock those items deep at every dealership.

It's not a big deal, you can change to DOT 4 as you wish.

 

[zumbooruk]

For what it's worth, this is from my research when I was looking for brake fluid.

I evaluated based on dry/web boiling point and hygroscopicity (if that's even a word) judged by manufacturer's recommended change interval, looking for change interval of more than 2 years which is the standard for DOT 5.1)

Bosch ESI6-32N Brake Fluid (DOT5.1)
https://www.amazon.com/Bosch-ESI6-32N-Brake-Direct-Replacement/dp/B07338GQM8
Dry Boiling Point: 270°C (518°F)
Wet Boiling Point: 185°C (365°F)
Cold viscosity at -40C: 670 mm2/s
Change Interval: 3 years

ATE Original Super DOT 5.1 Brake Fluid
https://www.amazon.com/ATE-Original-Super-Brake-Fluid/dp/B08P1QYLNP
Dry Boiling Point: 265°C (509°F)
Wet Boiling Point: 180°C (356°F)
Cold viscosity at -40C: 750 mm2/s
Change Interval: 3 years

ATE Original TYP 200 Racing Quality DOT 4 Brake Fluid
https://www.amazon.com/ATE-706202-Original-Racing-Quality/dp/B003VXRPL0
Dry Boiling Point: 280°C (536°F)
Wet Boiling Point: 198°C (388°F)
Cold viscosity at -40C: 1400 mm2/s
Change Interval: 2 years (some sources say up to 3 years)


Castrol SRF has the highest wet boiling point at 270°C and its silicon ester base reacts with moisture without major degradation, yet recommend change interval is only 18 months. though I've seen user reports of 3+ years for street use, not sure I can trust these, and therefore I eliminated it from consideration.

 

[Spart]

Castrol SRF has the highest wet boiling point at 270°C and its silicon ester base reacts with moisture without major degradation, yet recommend change interval is only 18 months. though I've seen user reports of 3+ years for street use, not sure I can trust these, and therefore I eliminated it from consideration.

If you track your car, you should never let any brake fluid go for three years.

Castrol SRF is great in that application in that it can get you through several track days and you can change it once a year. I (mistakenly) skipped a year in my GT350 once, and didn't notice a difference on track or off. Garaging the car extends the life of the fluid, too.

If you aren't tracking your car, those other fluids you mentioned will be just fine. I would note that DOT 4 tends to be higher viscosity and you may notice your clutch pedal being slower in the cold, so a low viscosity DOT 4 might be a good idea if that's an issue for you.

A really good all-rounder fluid I would shout out is Fuchs Titan DOT 514 LV. It's a combined DOT 5.1 and DOT 4 Low Viscosity spec. Pretty economical at $15/liter. Just hard to say anything bad about it, and you can use it in virtually everything. We originally bought it because it carried the spec for my buddy's Mercedes, but it's become our go-to.

 

[zumbooruk]

If you track your car, you should never let any brake fluid go for three years.

Castrol SRF is great in that application in that it can get you through several track days and you can change it once a year. I (mistakenly) skipped a year in my GT350 once, and didn't notice a difference on track or off. Garaging the car extends the life of the fluid, too.

If you aren't tracking your car, those other fluids you mentioned will be just fine. I would note that DOT 4 tends to be higher viscosity and you may notice your clutch pedal being slower in the cold, so a low viscosity DOT 4 might be a good idea if that's an issue for you.

A really good all-rounder fluid I would shout out is Fuchs Titan DOT 514 LV. It's a combined DOT 5.1 and DOT 4 Low Viscosity spec. Pretty economical at $15/liter. Just hard to say anything bad about it, and you can use it in virtually everything. We originally bought it because it carried the spec for my buddy's Mercedes, but it's become our go-to.

Thanks, did not occur to me to check viscosity!

Fuchs Titan DOT 514 LV
Dry Boiling Point: 270°C
Wet Boiling Point: 180°C
Cold viscosity at -40C: 750 mm2/s
Change Interval: 2 years

Bosch has lower viscosity, and longer recommended change interval (lower hygroscopicity)

Bosch ESI6-32N Brake Fluid (DOT5.1)
https://www.amazon.com/Bosch-ESI6-32N-Brake-Direct-Replacement/dp/B07338GQM8
Dry Boiling Point: 270°C (518°F)
Wet Boiling Point: 185°C (365°F)
Cold viscosity at -40C: 670 mm2/s
Change Interval: 3 years

ATE Original Super DOT 5.1 Brake Fluid
https://www.amazon.com/ATE-Original-Super-Brake-Fluid/dp/B08P1QYLNP
Dry Boiling Point: 265°C (509°F)
Wet Boiling Point: 180°C (356°F)
Cold viscosity at -40C: 750 mm2/s
Change Interval: 3 years

ATE Original TYP 200 Racing Quality DOT 4 Brake Fluid
https://www.amazon.com/ATE-706202-Original-Racing-Quality/dp/B003VXRPL0
Dry Boiling Point: 280°C (536°F)
Wet Boiling Point: 198°C (388°F)
Cold viscosity at -40C: 1400 mm2/s
Change Interval: 2 years (some sources say up to 3 years)

 

[Evox787]

For me, it’s like that Mr. Incredible meme but saying, “Fluid is fluid!” I honestly don’t think the way I drive my car will ever get me close to testing the boiling point. Still, I bought five 500 ml bottles of Motul RBF 660 because that’s the one I’ve been using since I got my Evo X and on my motorcycle. I usually replace it every year, but the process on these cars is so different and annoying that it’s been a year and a half, and I’m still running the stock fluid.

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