Dot 3 or Dot 4?
Thread Starter
Burning Brakes
Joined: Sep 2000
Posts: 1,063
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From: Long Island, New York
Dot 3 or Dot 4?
I wanted to change the clutch fluid and I was advised to replace it with dot 4 even though the filler cap says to use dot 3 is there a difference? also can I use the dot 4 in the brakes? 
Race Director
Joined: Jul 2004
Posts: 16,795
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From: Lake Havasu City, AZ
I have been using Valvoline Synpower Brake fluid it is both DOT 3 and DOT4. I use it in both the clutch and brake systems of both my Vettes.
IT has a higher boling point and less tendency to absorb water
IT has a higher boling point and less tendency to absorb water
Team Owner
Joined: Dec 1999
Posts: 34,873
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From: Lacey WA RVN 68-69
NCM Sinkhole Donor
GM does have a specific clutch hydraulic fluid (p/n 12345347)and that would be the best to use but otherwise a good DOT3 fluid works.
You can use DOT4 fluid in the brake system. DOT4 fluids typically have a higher wet and dry boiling point compared to DOT3 so if you do track days, autocross, or are extremely hard on the brakes, a good DOT 4 would be a good upgrade.
You can use DOT4 fluid in the brake system. DOT4 fluids typically have a higher wet and dry boiling point compared to DOT3 so if you do track days, autocross, or are extremely hard on the brakes, a good DOT 4 would be a good upgrade.
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
I use DOT4 brake fluid in the clutch. Higher boiling points.
Good DOT 4 brake fluid should have a wet not dry boiling point as close to if not above 400* F
Brand Wet Boiling Point Dry Boiling Point
DOT4
Castrol SRF 518°F 590°F
Motul 600 421°F 585°F
AP-600 410°F 572°F
ATE-Super Blue / Gold 392°F 536°F
------------------------- Above Line for track use
Valvoline SuperSyn 333°F 513°F
Castrol LMA 311°F 446°F
DOT 3
Ford HD 290°F 550°F
Wilwood 570 284°F 570°F
PFC-Z rated 284°F 550°F
AP-550 284°F 550°F
DOT Specifications:
DOT 3
Dry Boiling Point 401F
Wet Boiling Point 284F
DOT 4
Dry Boiling Point 446F
Wet Boiling Point 311F
Good DOT 4 brake fluid should have a wet not dry boiling point as close to if not above 400* F
Brand Wet Boiling Point Dry Boiling Point
DOT4
Castrol SRF 518°F 590°F
Motul 600 421°F 585°F
AP-600 410°F 572°F
ATE-Super Blue / Gold 392°F 536°F
------------------------- Above Line for track use
Valvoline SuperSyn 333°F 513°F
Castrol LMA 311°F 446°F
DOT 3
Ford HD 290°F 550°F
Wilwood 570 284°F 570°F
PFC-Z rated 284°F 550°F
AP-550 284°F 550°F
DOT Specifications:
DOT 3
Dry Boiling Point 401F
Wet Boiling Point 284F
DOT 4
Dry Boiling Point 446F
Wet Boiling Point 311F
Advanced
Joined: Aug 2005
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I'm not an expert on this by any means, but I've read that DOT 4 will eat rubber components and turn the fluid black. My personal experience seems to support that notion because I used DOT 4 in my '03 and couldn't keep the fluid clear regardless of how often I changed it. It turned black after a few days, and I went through nearly a quart, trying to get it to stay clear. So I'm sticking with the factory recommended fluid on my '04. 
Team Owner
Joined: Sep 2003
Posts: 43,084
Likes: 33
From: Raleigh / Rolesville NC
Originally Posted by Steve04Z06
I'm not an expert on this by any means, but I've read that DOT 4 will eat rubber components and turn the fluid black. My personal experience seems to support that notion because I used DOT 4 in my '03 and couldn't keep the fluid clear regardless of how often I changed it. It turned black after a few days, and I went through nearly a quart, trying to get it to stay clear. So I'm sticking with the factory recommended fluid on my '04.
Plus changing to stainless steel lines helps. no ss lines do not though 'codes' if attached properly.
I use Castrol SRF without any problems what so ever.
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Drifting
Joined: Jun 2002
Posts: 1,945
Likes: 41
From: Corinth TX
I haven't heard of any problems going from 3 to 4 but you shouldn't go to 5. I hope this link helps out a little as it did for me.
http://superchevy.com/technical/chas.../0509sc_fluid/
http://superchevy.com/technical/chas.../0509sc_fluid/
Team Owner
Joined: May 2001
Posts: 87,335
Likes: 1,590
From: Western NY
Originally Posted by rws.1
I have been using Valvoline Synpower Brake fluid it is both DOT 3 and DOT4. I use it in both the clutch and brake systems of both my Vettes.
IT has a higher boling point and less tendency to absorb water
IT has a higher boling point and less tendency to absorb water
Drifting
Joined: Jun 2002
Posts: 1,945
Likes: 41
From: Corinth TX
There is also a 610 brake fluid that is supposed to be really good. It was mentioned recently as being used in ALMS. It has a really high boiling point and does not contain silicone. BTW silicone is what is in DOT 5 that makes it incompatible with ABS systems.
Team Owner
Joined: Sep 2003
Posts: 43,084
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From: Raleigh / Rolesville NC
Originally Posted by NocarbutaVetteforme
There is also a 610 brake fluid that is supposed to be really good. It was mentioned recently as being used in ALMS. It has a really high boiling point and does not contain silicone. BTW silicone is what is in DOT 5 that makes it incompatible with ABS systems.
The Castrol SRF is $70-72 / liter. Think I am going to put that in my DD p-truck?? not a chance. but for the vette on the track darn straight. Boiled the Blue stuff too many times and have had brake fade as a result.
Normal Dot 3 or Dot 4 for street and occational spirited driving is fine.
Last edited by AU N EGL; Nov 28, 2005 at 07:43 AM.
Advanced
Joined: Aug 2005
Posts: 51
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Originally Posted by Bill Baird
I used DOT 4 brake fluid quite a bit in my 1975 coupe's brake system, and never had a problem with it hurting any rubber or of the fluid getting abnormally dirty.
