Brake Fluid - DOT 3 / DOT 4

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My '07 Hyundai Santa Fe calls for either DOT 3 or DOT 4 brake fluid (which I find strange--why not recommend one or the other?). Should I go with DOT 4 if changing the fluid? I am assuming DOT 4 is an improvement over DOT 3?

Thanks,
Ryan
 
If you routinely tow a trailer in very hilly mountains, it might be better to use DOT 4, but the DOT 3 should suffice. Little bit more resistance to boiling with the 4. Not much of a difference in price IMHO.
 
I don't have numbers off hand but IIRC the Motorcraft DOT 3 fluid has a little better boiling points than most... I avoid DOT4 as I have always heard that its even more hygroscopic than 3.
 
DOT 4 has a higher boiling point, but both will work. The most important thing is changing it every few years. Even Walmart DOT 3 will be sufficient. Kmart has their DOT 3 on sale for $4/qt.

That said, Castrol DOT 4 (used to be called LMA) is said to absorb moisture more slowly and thus last longer, but it's $10/qt and not as easy to find.

Valvoline DOT 3/4 that others have suggested also represents a good value.
 
Originally Posted By: KGMtech
If you routinely tow a trailer in very hilly mountains, it might be better to use DOT 4, but the DOT 3 should suffice. Little bit more resistance to boiling with the 4. Not much of a difference in price IMHO.

Or very high speed with a lot of hard braking like when you track your car, then DOT-4 is needed. Otherwise, DOT-3 is sufficient for normal everyday driving.

My E430 spec'ed DOT-4 but I replaced with DOT-3 since 2004-2005 and no problem what-so-ever. Main benefit is I need to bleed once every 3-4 years instead of 2 years.
 
I once saw somebody buying Dot 5. I had to ask them what the application was, as it is seldom used around here other than in collector cars.

They said it was just to top up, and thought 5 was better than 3 or 4 because it was more expensive.
 
Dot 5 is a SILOCONE based brake fluid. It WILL NOT mix with DOT 3 or 4 fluid and can lead to brake failure if mixed.

Worst thing in the world to use as a "top up" fluid.
 
Originally Posted By: ammolab
Dot 5 is a SILOCONE based brake fluid. It WILL NOT mix with DOT 3 or 4 fluid and can lead to brake failure if mixed.

Worst thing in the world to use as a "top up" fluid.
It will not cause brake failure.
 
Originally Posted By: CT8
Originally Posted By: ammolab
Dot 5 is a SILOCONE based brake fluid. It WILL NOT mix with DOT 3 or 4 fluid and can lead to brake failure if mixed.

Worst thing in the world to use as a "top up" fluid.
It will not cause brake failure.


No, it will not cause brake failier, but the fluid in the system would probably look like a Lava Lamp. Just not a good ide!

Then there is Dot 5.5
Is this confusing (to the lay person) or what?
 
Originally Posted By: CT8
[topping off with DOT 5] not cause brake failure.


Oh yes it will. The silicone DOES NOT play nice with the glycols used in DOT 3/4 and it will turn to goo. Even a small amount will cause the damage.
 
You call the shots. Personally I use DOT 4 Plus (or 5.1) in all my applications and replace the fluid annually, or every brake service if sooner.
 
Originally Posted By: buck91
I don't have numbers off hand but IIRC the Motorcraft DOT 3 fluid has a little better boiling points than most...


It's DRY boiling point (500*F) is much higher than other DOT 3s, and even than all of the 'on the shelf', inexpensive DOT 4s, except for the 'boutique', or racing fluids.

But it's WET boiling point is just at the DOT 3 standard, nothing great.
frown.gif
 
Originally Posted By: slacktide_bitog
Originally Posted By: CT8
[topping off with DOT 5] not cause brake failure.


Oh yes it will. The silicone DOES NOT play nice with the glycols used in DOT 3/4 and it will turn to goo. Even a small amount will cause the damage.
No it will cause any damage or turn to goo etc. It was covered in total when I did the ASE brake certification test for work. Besides at work there were braks systems that came with dot5 .There was a tag on the MC to use only dot 5 and the morons at work always topped off the fluid with dot 3 and there wasn't any problem and the engineers from the MFg sad it didn't really matter.
 
I use DOT4 LV, because it is said to improve ABS and traction control cycling times. I get Pentosin from NAPA and pay about $14 per liter.
 
Originally Posted By: CT8
Originally Posted By: slacktide_bitog
Originally Posted By: CT8
[topping off with DOT 5] not cause brake failure.


Oh yes it will. The silicone DOES NOT play nice with the glycols used in DOT 3/4 and it will turn to goo. Even a small amount will cause the damage.
No it will cause any damage or turn to goo etc. It was covered in total when I did the ASE brake certification test for work. Besides at work there were braks systems that came with dot5 .There was a tag on the MC to use only dot 5 and the morons at work always topped off the fluid with dot 3 and there wasn't any problem and the engineers from the MFg sad it didn't really matter.


Not doubting your certification, but did that training cover the fact that DOT 5 doesn't mix with DOT 3 or 4? Even the label on DOT 5 brake fluid cautions against mixing it. Won't necessarily turn to goo, but they separate like oil and water.
 
Honda Toyota Ford... dealers have excellent DOT-3 fluids. My Toyota is filled with DOT-4LV. My Hyundai is filled with Honda DOT3. Both work great.

I don't recommend DOT5. Use DOT 3, 4, 4LV, or 5.1

Just stick with a name brand fluid and don't worry about anything else. Its more important to bleed regularly(every year or 2) than to worry about the fanciest fluid out there.

Ignore anyone that claims mixing DOT 3/4 with DOT 5. I can not find any documentation where it states that DOT5 silicone can be safely mixed with DOT 3 glycol or DOT4 glycol/borate. I don't know of any engineers or manufacturers that would allow mixing. And, I can't find any ASE study guides that state that mixing silicone with glycol or borate is OK.
 
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