DOT Brake Fluid?
Logistics Pro
Joined: Nov 2011
Posts: 4,685
Likes: 80
From: Northville, MI
Greg, it looks like we are not any better here on FTE as far as consensus. Based upon Philip's linked article it looks like DOT 5.1 is glycol based so that it is compatible with DOT 3 & 4. Dot 5.0 is silicone based. As any painter will tell you, silicone becomes a real problem if there is a leak or spill.
I used DOT 5 on a '49 Jeepster that I restored but after I painted it. On my current project I have gone with DOT 4 particularly since I knew that I was going to paint things piecemeal since I do not have a spray booth.
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I used DOT 5 on a '49 Jeepster that I restored but after I painted it. On my current project I have gone with DOT 4 particularly since I knew that I was going to paint things piecemeal since I do not have a spray booth.
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Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
Greg, it looks like we are not any better here on FTE as far as consensus. Based upon Philip's linked article it looks like DOT 5.1 is glycol based so that it is compatible with DOT 3 & 4. Dot 5.0 is silicone based. As any painter will tell you, silicone becomes a real problem if there is a leak or spill.
I used DOT 5 on a '49 Jeepster that I restored but after I painted it. On my current project I have gone with DOT 4 particularly since I knew that I was going to paint things piecemeal since I do not have a spray booth.
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I used DOT 5 on a '49 Jeepster that I restored but after I painted it. On my current project I have gone with DOT 4 particularly since I knew that I was going to paint things piecemeal since I do not have a spray booth.
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Dot 4 is Gylcol/Borate Ester based
Dot 5.1 is Borate Ester/ Glycol based
And of course Dot 5 is silicone.
Conventional brake fluids are all backwards compatible Meaning you can use Dot 5.1 in a Dot 4 or 3 system. Or Dot 4 in a Dot 3 system.
They are NOT forward compatible You cannot use Dot 3 in a Dot 4 or Dot 5.1 System or Dot 4 in a Dot 5.1 system.
If you want to use conventional fluid in your truck go with Dot 5.1 as you can then extended fluid changes out to every 3 years from the standard 2.
Fleet Owner
Joined: Dec 2000
Posts: 25,374
Likes: 5,383
From: Central PA
Dot 3 fluid is Glycol based.
Dot 4 is Gylcol/Borate Ester based
Dot 5.1 is Borate Ester/ Glycol based
And of course Dot 5 is silicone.
Conventional brake fluids are all backwards compatible Meaning you can use Dot 5.1 in a Dot 4 or 3 system. Or Dot 4 in a Dot 3 system.
They are NOT forward compatible You cannot use Dot 3 in a Dot 4 or Dot 5.1 System or Dot 4 in a Dot 5.1 system.
If you want to use conventional fluid in your truck go with Dot 5.1 as you can then extended fluid changes out to every 3 years from the standard 2.
Dot 4 is Gylcol/Borate Ester based
Dot 5.1 is Borate Ester/ Glycol based
And of course Dot 5 is silicone.
Conventional brake fluids are all backwards compatible Meaning you can use Dot 5.1 in a Dot 4 or 3 system. Or Dot 4 in a Dot 3 system.
They are NOT forward compatible You cannot use Dot 3 in a Dot 4 or Dot 5.1 System or Dot 4 in a Dot 5.1 system.
If you want to use conventional fluid in your truck go with Dot 5.1 as you can then extended fluid changes out to every 3 years from the standard 2.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Originally Posted by GreatNorthWoods
IT???? "It" is Dot 5 which if you had read the entire thread you would have known what "it" is.
One thing about flushing the brake lines periodically it does give the operator an opportunity whether he wants it or not to get under the truck and look stuff over, never a bad idea. Speedbleeders work real slick with the one-way checkball, and even a gravity bleed works easey-peasey.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
Originally Posted by abe
Thanks for posting that I was just going to ask what's the difference between 3 and 4. So now my question is, what is Borate/Ester?
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
DOT 3 is not recommended for Anti Lock use because of it's lower boiling point.
In passenger use Anti lock brakes will generate far more heat than standard brakes. In terms of viscosity at high temps it is just about twice as thin as DOT 4 and about 35% thicker at low temps, so it has a greater chance of seeping past seals in anti lock pumps when warmed up, Plus it is far more hygroscopic increasing the risk of corrosion damage in delicate anti-lock components.
Not mentioned there is also Dot 4+ (aka Dot 4 Super)
It has more less been superseded by Dot 5.1, as it is near identical to Dot 5.1 in terms of viscosity boiling point, hygroscopy and chemical composition.
Lead Driver
Joined: Aug 2002
Posts: 6,682
Likes: 12
From: Saskatoon SK Canada
I have never came across any vehicle that has left the factory with DOT 5 or 5.1. I've only seen it on motorcycles. Pick any normal domestic or Asian vehicle and it comes equipped with DOT 3 fluid. Only the European vehicles come with DOT 4.
For example, Ford uses a DOT 3 HD fluid. When its brand new the boiling point is actually higher than DOT 4 but once it gets old with some moisture, its the same as DOT 3.
At work, we get DOT 3 by the pail and can only get DOT 4 in 2 liter jugs. I've seen many customer vehicles with contaminated brakes systems from oil, washer fluid, you name it. Only once have I seen a vehicle were they cooked the brake fluid. It was on a 2008 Ford F-150 where they put the front pads in backwards. The rotor was the same colour as the emblem on the front. With the pressure bleeder hooked up, the brake fluid came out looking like yellow snot.
Honestly DOT 3 or 4 is simple, available everywhere, cheap and works fine. I'm only going to put DOT 4 in my 1951 and it has much bigger brakes than most people on here.
For example, Ford uses a DOT 3 HD fluid. When its brand new the boiling point is actually higher than DOT 4 but once it gets old with some moisture, its the same as DOT 3.
At work, we get DOT 3 by the pail and can only get DOT 4 in 2 liter jugs. I've seen many customer vehicles with contaminated brakes systems from oil, washer fluid, you name it. Only once have I seen a vehicle were they cooked the brake fluid. It was on a 2008 Ford F-150 where they put the front pads in backwards. The rotor was the same colour as the emblem on the front. With the pressure bleeder hooked up, the brake fluid came out looking like yellow snot.
Honestly DOT 3 or 4 is simple, available everywhere, cheap and works fine. I'm only going to put DOT 4 in my 1951 and it has much bigger brakes than most people on here.
Freshman User
Joined: Jan 2016
Posts: 48
Likes: 1
From: Lowell, MI
I just bought a a low mileage recently refreshed 57 Ford with excellent working brakes. From a collector. contemplating converting to dual master cylinder. How do I tell what type of brake fluid is in it??
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Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
I have never came across any vehicle that has left the factory with DOT 5 or 5.1. I've only seen it on motorcycles. Pick any normal domestic or Asian vehicle and it comes equipped with DOT 3 fluid. Only the European vehicles come with DOT 4.
For example, Ford uses a DOT 3 HD fluid. When its brand new the boiling point is actually higher than DOT 4 but once it gets old with some moisture, its the same as DOT 3.
At work, we get DOT 3 by the pail and can only get DOT 4 in 2 liter jugs. I've seen many customer vehicles with contaminated brakes systems from oil, washer fluid, you name it. Only once have I seen a vehicle were they cooked the brake fluid. It was on a 2008 Ford F-150 where they put the front pads in backwards. The rotor was the same colour as the emblem on the front. With the pressure bleeder hooked up, the brake fluid came out looking like yellow snot.
Honestly DOT 3 or 4 is simple, available everywhere, cheap and works fine. I'm only going to put DOT 4 in my 1951 and it has much bigger brakes than most people on here.
For example, Ford uses a DOT 3 HD fluid. When its brand new the boiling point is actually higher than DOT 4 but once it gets old with some moisture, its the same as DOT 3.
At work, we get DOT 3 by the pail and can only get DOT 4 in 2 liter jugs. I've seen many customer vehicles with contaminated brakes systems from oil, washer fluid, you name it. Only once have I seen a vehicle were they cooked the brake fluid. It was on a 2008 Ford F-150 where they put the front pads in backwards. The rotor was the same colour as the emblem on the front. With the pressure bleeder hooked up, the brake fluid came out looking like yellow snot.
Honestly DOT 3 or 4 is simple, available everywhere, cheap and works fine. I'm only going to put DOT 4 in my 1951 and it has much bigger brakes than most people on here.
All MILCOTS (military commercial off the shelf) vehicles supplied to the US military come equipped with Dot 5 utilizing all the same components as the civillian units. So yes Domestic stuff certainly does come equipped with DOT 5
All new Fords are equipped with Dot 4
See below fluid specifications for 2017 Fords.
Post Fiend
Joined: Feb 2008
Posts: 5,831
Likes: 121
From: St Albert, Alberta
DOT 3 is available in clear, Pale Yellow, Blue & Crimson Red ,
DOT 4 is available in Clear, Pale Yellow & Crimson Red
DOT 5.1 is available Clear, Pale Yellow & Blue
DOT 5 is available in Purple (Mil-PRF-46176 & Mil-PRF-46176B) & Violet
Mountain Pass
Joined: Oct 2017
Posts: 116
Likes: 63
This is what I know based on my racing experience:
The more marginal your braking system, the better brake fluid you need.
When I first started out racing my 911 I had stock brakes and street pads with DOT3 fluid. After 3-4 hot laps at our local 1.2 mile road course, I would start to get brake fade.
I upgraded my fluid to DOT 5.1 and never had issues with brake fade again however, once hot my braking was not as good after about 10 laps. My next move was to upgrade my pads to racing pads. This system worked well and I completely resolved my brake fade issues.
One day at the track, I was making a change to my front suspension and had to crack a brake line. I switched to ATE Super Blue - it was all we had in our pit stall and in the Porsche community was considered a performance brake fluid.
I went out on the track and within 3 laps had ‘Brown trouser’ brake fade again. It was terrifying. I came into the pits and parked it for the day.
I changed my fluid to Brembo LCF600plus and ran this product for the next 2 seasons (changing at the end of the season) without any issues.
My next move was to upgrade my braking system to Porsche 917 style calipers and rotors and a bigger master cylinder. I was in a hurry and didn’t have Brembo LCF600plus so I ran the ATE Super Blue for my first practice day and it worked fine with no fade. This new brake system could really shed heat, unlike the stock Porsche calipers and rotors. I was also running street pads. The braking performance wasn’t a whole bunch better than my stock system was with the racing pads according to my telemetry so I upgraded to Pagid Yellow RS29 endurance racing pads and switched my brake fluid to Brembo LCF600PLUS. The brakes in that car are now the nicest brakes in any car I have ever driven.
In my endurance race cars, we have to run a ‘stock’ system but are allowed racing pads. We use the Brembo
LCF600PLUS fluid there and have never had issues.
A lower cost alternative is to run the Ford heavy duty brake fluid and change it after each race day because while it has a good dry boiling point, it has a low wet boiling point.
If you live in a moist climate and use your brakes heavily, you need a brake fluid with a decent wet boiling point. If you have a marginal (1950s) braking system, a real performance brake fluid will make a huge difference. All brake pads / shoes are not created equally. In my street vehicles, I am a big fan of the Powerstop Evolution Plus products. I currently have a set of the Evolution Z23 pads in my daily driver pickup (ordered by mistake) that is used extensively for HEAVY towing and they seem ok too.
And change your brake fluid regularly. Despite what has been posted above, your master cylinder has to be vented to atmosphere. If it wasn’t, as your pads wear and the fluid level in the reservoir drops, it would draw a vacuum in the reservoir... this atmospheric vent allows moist air into the system which leads to water contamination. This is a drawback to having the master cylinder mounted under the floor boards if your truck ever sees rain or wet roads.
The more marginal your braking system, the better brake fluid you need.
When I first started out racing my 911 I had stock brakes and street pads with DOT3 fluid. After 3-4 hot laps at our local 1.2 mile road course, I would start to get brake fade.
I upgraded my fluid to DOT 5.1 and never had issues with brake fade again however, once hot my braking was not as good after about 10 laps. My next move was to upgrade my pads to racing pads. This system worked well and I completely resolved my brake fade issues.
One day at the track, I was making a change to my front suspension and had to crack a brake line. I switched to ATE Super Blue - it was all we had in our pit stall and in the Porsche community was considered a performance brake fluid.
I went out on the track and within 3 laps had ‘Brown trouser’ brake fade again. It was terrifying. I came into the pits and parked it for the day.
I changed my fluid to Brembo LCF600plus and ran this product for the next 2 seasons (changing at the end of the season) without any issues.
My next move was to upgrade my braking system to Porsche 917 style calipers and rotors and a bigger master cylinder. I was in a hurry and didn’t have Brembo LCF600plus so I ran the ATE Super Blue for my first practice day and it worked fine with no fade. This new brake system could really shed heat, unlike the stock Porsche calipers and rotors. I was also running street pads. The braking performance wasn’t a whole bunch better than my stock system was with the racing pads according to my telemetry so I upgraded to Pagid Yellow RS29 endurance racing pads and switched my brake fluid to Brembo LCF600PLUS. The brakes in that car are now the nicest brakes in any car I have ever driven.
In my endurance race cars, we have to run a ‘stock’ system but are allowed racing pads. We use the Brembo
LCF600PLUS fluid there and have never had issues.
A lower cost alternative is to run the Ford heavy duty brake fluid and change it after each race day because while it has a good dry boiling point, it has a low wet boiling point.
If you live in a moist climate and use your brakes heavily, you need a brake fluid with a decent wet boiling point. If you have a marginal (1950s) braking system, a real performance brake fluid will make a huge difference. All brake pads / shoes are not created equally. In my street vehicles, I am a big fan of the Powerstop Evolution Plus products. I currently have a set of the Evolution Z23 pads in my daily driver pickup (ordered by mistake) that is used extensively for HEAVY towing and they seem ok too.
And change your brake fluid regularly. Despite what has been posted above, your master cylinder has to be vented to atmosphere. If it wasn’t, as your pads wear and the fluid level in the reservoir drops, it would draw a vacuum in the reservoir... this atmospheric vent allows moist air into the system which leads to water contamination. This is a drawback to having the master cylinder mounted under the floor boards if your truck ever sees rain or wet roads.
Thread Starter
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Fleet Mechanic
Joined: Jun 2015
Posts: 1,874
Likes: 295
From: Central Michigan
Well, a lot of good info here, thanks so much to all of you. My Cutlass is similar to what your vehicle you talk of, Matthew, DOT 5 been in it for 20 yrs and no troubles or issues. I also have a 2002 Impala (not anti-lock) that has 300,000 miles on it that has never had the hydraulic part of the brakes opened and still has the original GM 2002 fluid in it, with no troubles. I'll bet that fluid has some water in it! So the jury is still out on the decision. Keep the comments, advice coming!!