So today I brought my mom's Camry to the mechanic for a brake flush (which ended up including a brake job because the right front pad was worn, but that's for another thread) and the mechanic used DOT4 and I think the car came with DOT3. I'm not really worried or anything but what's the difference between the two besides the boiling points?
difference between DOT3 & DOT4?
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There is nothing wrong with using Dot 4 instead of Dot 3. Consider this an upgrade as they have higher boiling points.
The only downside from what I recall is that Dot 4 possibly absorbs moisture quicker than Dot 3 but am not 100% sure about this info.
The only downside from what I recall is that Dot 4 possibly absorbs moisture quicker than Dot 3 but am not 100% sure about this info.
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DOT 3 absorbs faster. also Dot 4 is slightly thicker. Many European vehicles require DOT 4, such as my Volvo. it especially helps with an ABS controlled traction control system
The DOT 4 is generally thicker than DOT 3, so if you live in area with cold winter and the car is using ABS, the ABS may not work properly.
That is why they invent DOT 5.1 or Super Dot 4 for people want better fluid than DOT 3 and still maintain ABS work on winter.
This ABS may not an issue if the car is designed to use DOT 4 from the manufacturer.
That is why they invent DOT 5.1 or Super Dot 4 for people want better fluid than DOT 3 and still maintain ABS work on winter.
This ABS may not an issue if the car is designed to use DOT 4 from the manufacturer.
Check out ATE SL.6 if you want a DOT4 that still is compatible with ABS systems. Looks like they developed it specifically for this reason.
I have been using Valvoline Synpower (exceeds DOT4) in all my DOT 3 cars with ABS and it works very well. I know they discontinued it but I found a stash at a Discount Drug Mart and bought it all. So I have enough for a year.
The higher the DOT number, the higher the wet boiling point.
DOT4 is the same basic chemistry (polyglycol ether) as DOT3, but has slightly different ingredients to provide that higher wet boiling point. In a very few cases it might be incompatible with some of the materials of the brake system. I've switched everything to DOT4 for years with no problems at all.
DOT4+ and DOT5.1 are again the same basic chemistry but slightly different for an even higher wet boiling point. They meet the same spec (the DOT5 spec) despite the different names.
DOT5 is silicone base and must never be switched into a system not made for silicone brake fluid.
DOT3 absorbs water faster. Ford's DOT3 is a popular brake fluid for amateur racers because of its very high dry boiling point, and as long as the fluid is changed very frequently, works very well. It is not as suitable for long term use as a DOT4 fluid nor some of the better DOT3 fluids.
By the way, don't be hyped about synthetic brake fluid...they are ALL synthetic.
DOT4 is the same basic chemistry (polyglycol ether) as DOT3, but has slightly different ingredients to provide that higher wet boiling point. In a very few cases it might be incompatible with some of the materials of the brake system. I've switched everything to DOT4 for years with no problems at all.
DOT4+ and DOT5.1 are again the same basic chemistry but slightly different for an even higher wet boiling point. They meet the same spec (the DOT5 spec) despite the different names.
DOT5 is silicone base and must never be switched into a system not made for silicone brake fluid.
DOT3 absorbs water faster. Ford's DOT3 is a popular brake fluid for amateur racers because of its very high dry boiling point, and as long as the fluid is changed very frequently, works very well. It is not as suitable for long term use as a DOT4 fluid nor some of the better DOT3 fluids.
By the way, don't be hyped about synthetic brake fluid...they are ALL synthetic.
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DOT 3 absorbs H2O faster than DOT 4. BUTTTTTTT (and that's a very big butt) according to these sources, there is somewhat of a conundrum here. For an equal absorption of of moisture, lets say 2%, the boiling point of the DOT 4 drops off at a MUCH greater rate than the DOT 3.
Read the details here: http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml
"DOT 4 fluids are also glycol ether based, but have a measure of borate esters thrown in for improved properties including increased dry and wet boiling points. 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. By FMVSS116 standards, DOT 4 fluids must have a minimum dry boiling point of 446F and a minimum wet boiling point of 311F.
Does this make DOT 4 fluids better than DOT 3 fluids? Not always. Remember, the boiling points listed are minimums and there are DOT 3 fluids out there with higher boiling points than some DOT 4 fluids. The real differentiating factor should be that if you run a DOT 4 fluid you really should change the fluid more often than if you use a DOT 3, if for no other reason than the rapid fall off in boiling point with time."
This article says the same:
http://www.aa1car.com/library/bfluid.htm
"Only one percent water in the fluid can lower the boiling point of a typical DOT 3 fluid to 369 degrees. Two percent water can push the boiling point down to around 320 degrees, and three percent will take it all the way down to 293 degrees, which is getting dangerously close to the minimum DOT and OEM requirements.
DOT 4 fluid, which has a higher minimum boiling temperature requirement (446 degrees F dry and 311 degrees wet) soaks up moisture at a slower rate but suffers an even sharper drop in boiling temperature as moisture accumulates. Three percent water will lower the boiling point as much as 50%!"
So, there are trade offs when comparing the two. I follow the manufacturers recommendation in my daily driver. As mentioned, there "might" be concerns with the borate esters and viscosity differences. I wonder why valvolene dropped their popular Syn Power Dot 4?
These are both good reads. Enjoy
Read the details here: http://www.stoptech.com/tech_info/wp_brakefluid_1a.shtml
"DOT 4 fluids are also glycol ether based, but have a measure of borate esters thrown in for improved properties including increased dry and wet boiling points. 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. By FMVSS116 standards, DOT 4 fluids must have a minimum dry boiling point of 446F and a minimum wet boiling point of 311F.
Does this make DOT 4 fluids better than DOT 3 fluids? Not always. Remember, the boiling points listed are minimums and there are DOT 3 fluids out there with higher boiling points than some DOT 4 fluids. The real differentiating factor should be that if you run a DOT 4 fluid you really should change the fluid more often than if you use a DOT 3, if for no other reason than the rapid fall off in boiling point with time."
This article says the same:
http://www.aa1car.com/library/bfluid.htm
"Only one percent water in the fluid can lower the boiling point of a typical DOT 3 fluid to 369 degrees. Two percent water can push the boiling point down to around 320 degrees, and three percent will take it all the way down to 293 degrees, which is getting dangerously close to the minimum DOT and OEM requirements.
DOT 4 fluid, which has a higher minimum boiling temperature requirement (446 degrees F dry and 311 degrees wet) soaks up moisture at a slower rate but suffers an even sharper drop in boiling temperature as moisture accumulates. Three percent water will lower the boiling point as much as 50%!"
So, there are trade offs when comparing the two. I follow the manufacturers recommendation in my daily driver. As mentioned, there "might" be concerns with the borate esters and viscosity differences. I wonder why valvolene dropped their popular Syn Power Dot 4?
These are both good reads. Enjoy
I have heard this argument repeatedly but never understood it. IIRC, BP may drop off faster for DOT4 but its a moot point because BP will pretty much always be higher than a DOT3 for a given percent moisture.
I always replace the DOT3 in my parent's cars with DOT4. It always make the pedal easier to push due to lower viscosity, and the fluid always stays cleaner.
I have always been told that DOT4 absorbs moisture more quickly than DOT3, but my experience has proved otherwise. My guess is that DOT3 can be made with some cheap stuff, but making DOT4 requires something more expensive.
I have always been told that DOT4 absorbs moisture more quickly than DOT3, but my experience has proved otherwise. My guess is that DOT3 can be made with some cheap stuff, but making DOT4 requires something more expensive.
arti - The DOT 4 is thicker.
I wonder where the moisture is coming from in modern sealed brake systems?
From the minute of exposure to air when you are filling it?
1-2% is a huge amount of water to be in a brake system.
I can't see it happening, unless there are massive problems otherwise, and fluid is not you biggest concern then.
From the minute of exposure to air when you are filling it?
1-2% is a huge amount of water to be in a brake system.
I can't see it happening, unless there are massive problems otherwise, and fluid is not you biggest concern then.
There is no such thing as a perfectly sealed system. The moisture comes in with air from around the seals as they are exercised, especially the caliper piston seals and the wheel cylinder seals. The older and harder the seals get, the more they allow minute quantities of air to pass. They don't have to leak fluid for this to happen.
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