DOT3 vs DOT4 Brake Fluid

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2,721
Location
MURICA
There's a temperature difference between DOT3 and DOT4, but would there be any harm for any grandpa type of driving to use DOT3 instead of DOT4?

Thanks for the help.
 
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11,178
Location
USA
There's nothing wrong with using DOT3, but Walmart has DOT4 at a good price :)

However, it's more important that it's changed regularly rather than what kind you use, whether you choose DOT 3, DOT 4, Walmart brand, name brand, etc.
If you want something you don't have to worry about for a long time, consider Castrol DOT4 "LMA" or Bosch ESI6 which are supposed to last longer
 
Messages
2,090
Location
missouri
I think you got that backwards, dot 3 absorbs moisture slower, and is less expensive. This is why non-performance cars tend to use Dot 3.

There are additives for corrosion. You could assume name brands have effective additives, that can be wrong.

There are also low viscosity fluids in both Dot 3 and Dot 4, I do not know if they absorb quicker or slower.

Rod
 
Messages
23,410
Location
CA
I think you got that backwards, dot 3 absorbs moisture slower, and is less expensive. This is why non-performance cars tend to use Dot 3.

There are additives for corrosion. You could assume name brands have effective additives, that can be wrong.

There are also low viscosity fluids in both Dot 3 and Dot 4, I do not know if they absorb quicker or slower.

Rod
Correct. While there are certain brands of DOT4 and DOT4LV that claim to absorb less moisture (and last longer), a blanket statement should not be made.
 
Messages
530
Location
Canada
DOT4 is higher performance (boiling point) than DOT3, but it also deteriorates faster since it absorbs water more readily. Past a certain water content, DOT4 will become lower performance than DOT3. For the average daily driver, I would say stick with DOT3 unless you're going to be religiously flushing it out every 2 years.
 
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4,692
Location
Southeast
This will probably get some weird looks, but dot 3 has provided me with a firmer pedal feel than dot 4. for years I just figured if I said that, 500 guys on a forum would tell me I had a knack for poorly bleeding dot 4 fluid. But not too long ago I admitted it in a bitog recovery group and several others admitted they had the same experience. I just go with what’s on the reservoir lid. Brakes are so well cooled these days I’ve smoked pads before boiling fluid.
 
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1,543
Location
UT
DOT4 is higher performance (boiling point) than DOT3, but it also deteriorates faster since it absorbs water more readily. Past a certain water content, DOT4 will become lower performance than DOT3. For the average daily driver, I would say stick with DOT3 unless you're going to be religiously flushing it out every 2 years.

Not necessarily true. Once again, a blanket statement that does not accurately represent many DOT4 brake fluid formulations that absorb moisture at a slower rate than most DOT3 products.

It would be fair to say that, generally speaking, many DOT4 products will absorb moisture quicker than most DOT3 products. But for those that regularly bleed the brakes on their cars, this is a non-issue. It's not like DOT4 is going to go bad in a year, or even two or three.

I use ATE200 or Bosch DOT3 / 4 / 5.1 products in both my cars. When I check the brake fluid with a meter, before doing a 30k mile brake fluid bleed, the meter doesn't even measure any moisture. I could more than safely go 4 years or more before measuring enough moisture to warrant a brake fluid bleed. In fact, Bosch DOT3 / 4 / 5.1 is formulated to last 100% longer than DOT3 products.

But, to answer the OP's question, DOT3 will work fine in a daily driver that never sees extreme conditions, such as towing, high speeds, or long, steep declines.
 
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7,931
Location
MI
This old Stop Tech blanket statement article approaches the debate in even a different way than expressed above:

"A seldom talked about characteristic though is that because of this chemistry, the DOT 4 fluid will have a more stable and higher boiling point during the early portion of its life, but ironically once the fluid does actually begin to absorb water its boiling point will typically fall off more rapidly than a typical DOT 3. "


At least I have this one aspect of my vehicles that OCD does not interfer with - I use what my manuals recommend, always DOT 3 so far.
 
Messages
5,015
Location
Ohio
There's a temperature difference between DOT3 and DOT4, but would there be any harm for any grandpa type of driving to use DOT3 instead of DOT4?

Thanks for the help.
DOT 3 is fine and that's all I use and if that is what your manufacturer recommends, you will be fine.. Going to Pike's Peak often, I might want DOT 4.
 
Messages
11,683
Location
Colorado Springs
DOT3 in general absorbs less moisture. But, that is just part of the story. What is important is to change fluid regularly and pay attention to wet boiling point if fluid is used longer.
I personally use strictly ATE TYP200 DOT4 fluid in all three of my vehicles. It is basically track suitable fluid with dry point of 280c and wet 198c. Now, why wet is important? Wet boiling point is measured at 3% of moisture in fluid. So, regardless that ATE TYP200 probably absorbs moisture more (it is more hygroscopic) it has such high wet boiling point that it would outperform at 3% moisture any DOT3 brake fluid.
However, as stated, in 2 years, no brake fluid should reach 3% moisture level, regardless of hygroscopic level.
Now, regarding grandpa driving style. Here in Colorado, going downhill most issues with brake overheating have people how drive like grandpa, resting their foot on brake while going downhill, like it is some love affair between them and brake pedal.
So, you will be safe with either I would say, but I would always go DOT4 and more importantly, change it every 2-3 years.
 
Messages
7,684
Location
The Midwest
There are two types of DOT 4 brake fluid DOT 4 and DOT 4LV. LV is low viscosity. DOT 4LV has been/is used in many new Ford vehicle's, every F150 included. Euro makes also switched to DOT 4LV.
 
Messages
3,283
Location
West Michigan
Any thoughts on the valvoline “synthetic” dot 3&4 fluid? I’ve been using it for years and it’s always been fine but I can’t seem to find any actual specs on it now. Just their separate dot 3 and dot 4 fluids.
 
Messages
25,448
Location
MA, Mittelfranken.de
Any thoughts on the valvoline “synthetic” dot 3&4 fluid? I’ve been using it for years and it’s always been fine but I can’t seem to find any actual specs on it now. Just their separate dot 3 and dot 4 fluids.

I put it in everything Euro, Japanese and domestic alike, never had a problem with it. It is a good all rounder for DD vehicles with no special requirements like LV or special spec fluid.
 
Messages
11,683
Location
Colorado Springs
There are two types of DOT 4 brake fluid DOT 4 and DOT 4LV. LV is low viscosity. DOT 4LV has been/is used in many new Ford vehicle's, every F150 included. Euro makes also switched to DOT 4LV.
Almost all manufacturers use DOT4LV in their higher performance vehicles or their all models (BMW, VW, etc.). Reason is better ESP operation at lower temperatures. However, LV fluids should not be used on track and similar environment ever.
 
Messages
11,178
Location
USA
Almost all manufacturers use DOT4LV in their higher performance vehicles or their all models (BMW, VW, etc.). Reason is better ESP operation at lower temperatures. However, LV fluids should not be used on track and similar environment ever.

What's wrong with using LV on the track?
 
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