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Is there any advantage to DOT3 over DOT4? #4976553
01/11/19 10:18 PM
01/11/19 10:18 PM
Joined: Sep 2009
Posts: 200
Rapid City, South Dakota
littlehulkster Offline OP
littlehulkster  Offline OP

Joined: Sep 2009
Posts: 200
Rapid City, South Dakota
I need a brake flush in my 2015 Mazda3, and while the manual specifies DOT3, I have a large unopened bottle of DOT4 I had bought for a future job on my old car. I understand that DOT4 can be used in any application where DOT3 is specified without harm, but I was also thinking that since this car is a 2015, Mazda could have specced it for DOT4 in the manual but didn't, and DOT4 is not even mentioned. However, it seems that DOT4 is a flatly superior product.

Is there some sort of advantage to DOT3 over DOT4 that I'm not aware of, or was the DOT3 spec just a matter of cost? I guess to rephrase the question, I know I CAN use DOT4, but SHOULD I?


2015 Mazda3 I 2.0
Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976568
01/11/19 10:34 PM
01/11/19 10:34 PM
Joined: Mar 2008
Posts: 7,925
USA
slacktide_bitog Offline
slacktide_bitog  Offline

Joined: Mar 2008
Posts: 7,925
USA
Yes, use the DOT 4 smile

Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976569
01/11/19 10:36 PM
01/11/19 10:36 PM
Joined: Jul 2005
Posts: 31,714
NY
demarpaint Offline
demarpaint  Offline

Joined: Jul 2005
Posts: 31,714
NY
I'd use the DOT 4.


God Bless Our Troops

Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976597
01/11/19 11:16 PM
01/11/19 11:16 PM
Joined: Apr 2016
Posts: 1,162
KS
FordBroncoVWJeta Offline
FordBroncoVWJeta  Offline

Joined: Apr 2016
Posts: 1,162
KS
DOT4 is superior.


2017 Volkswagen Jetta 1.4T - 2015 Honda CRV 2.4 - 2012 Volkswagen Jetta 2.0 - 2007 Chevy Trailblazer 4.2 - 2001 Pontiac Sunfire 2.2
Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976603
01/11/19 11:26 PM
01/11/19 11:26 PM
Joined: Apr 2012
Posts: 6,345
MA
Wolf359 Offline
Wolf359  Offline

Joined: Apr 2012
Posts: 6,345
MA
Yes, the only real difference is the cost, Dot 4 can be about double or so the price of Dot 3. Only reason for Dot 3 would be that the car isn't high powered and the brakes won't really be taxed so there's no need for the higher boiling points of Dot 4. But if you already have it, go ahead and use it.

Re: Is there any advantage to DOT3 over DOT4? [Re: Wolf359] #4976605
01/11/19 11:31 PM
01/11/19 11:31 PM
Joined: Sep 2009
Posts: 200
Rapid City, South Dakota
littlehulkster Offline OP
littlehulkster  Offline OP

Joined: Sep 2009
Posts: 200
Rapid City, South Dakota
Originally Posted by Wolf359
Yes, the only real difference is the cost, Dot 4 can be about double or so the price of Dot 3. Only reason for Dot 3 would be that the car isn't high powered and the brakes won't really be taxed so there's no need for the higher boiling points of Dot 4. But if you already have it, go ahead and use it.


I guess I have to wonder why DOT3 is even sold anymore, then. Sure, 4 costs more, but brake fluid is cheap overall. The cost of using DOT4 over 3 may be 2x, but 2x 5 is only 10.


2015 Mazda3 I 2.0
Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976623
01/12/19 12:05 AM
01/12/19 12:05 AM
Joined: Apr 2012
Posts: 6,345
MA
Wolf359 Offline
Wolf359  Offline

Joined: Apr 2012
Posts: 6,345
MA
Well the manufacturers watch every penny. Some recalls are caused by penny pincher that shave a few cents off the cost of a part. If you save $5 extra per car and sell 100k, that's a $500k savings. A few dollars here and there can add up to millions without raising the price.

Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976676
01/12/19 03:33 AM
01/12/19 03:33 AM
Joined: Oct 2017
Posts: 189
MI
HorseThief Offline
HorseThief  Offline

Joined: Oct 2017
Posts: 189
MI
They taste the same to me....


I saw a brown dog
Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976811
01/12/19 09:42 AM
01/12/19 09:42 AM
Joined: Nov 2011
Posts: 1,486
Lyndhurst NJ
Audios Offline
Audios  Offline

Joined: Nov 2011
Posts: 1,486
Lyndhurst NJ
DOT 3 is less likely to absorb water and can usually go longer in the system before changing. However 4 is the better fluid.


2002 VW Golf TDI-Mobil 1 5/40 TDT
2007 Mercedes GL320 CDI- M1 0/30 ESP
2005 BMW M3 BMW Twin Power 10/60
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1998 BMW M3/4/5 Fuchs 5/40
Re: Is there any advantage to DOT3 over DOT4? [Re: Audios] #4976828
01/12/19 09:58 AM
01/12/19 09:58 AM
Joined: Feb 2013
Posts: 1,257
Prospect, KY
spk2000 Offline
spk2000  Offline

Joined: Feb 2013
Posts: 1,257
Prospect, KY
Originally Posted by Audios
DOT 3 is less likely to absorb water and can usually go longer in the system before changing. However 4 is the better fluid.


Have heard this more than once but never saw anything that proves it is true and not just rumor. Anyone got some studies or evidence?


96 Grand Marquis
01 Sable LS
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Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4976845
01/12/19 10:22 AM
01/12/19 10:22 AM
Joined: Dec 2013
Posts: 292
Virginia
Dufus2 Offline
Dufus2  Offline

Joined: Dec 2013
Posts: 292
Virginia
I used DOT 4 from Napa and it seems to be a little thicker, in very cold weather DOT 4 may be slower to respond. I just use the Walmart SuperTech DOT 3 brake fluid (paid $5 for a quart) and change it out every 2-3 years depending upon the condition. I just bought a brake fluid tester pen and my old fluid tested at 1-2% moisture after at least two years.


ASE Certified in Med/Heavy Truck Service including A9
Heavy Equipment Repair, Fleet Maintenance
Real Cars Rattle and Smoke a Little
Re: Is there any advantage to DOT3 over DOT4? [Re: Dufus2] #4976854
01/12/19 10:30 AM
01/12/19 10:30 AM
Joined: Apr 2017
Posts: 1,522
Ontario, Canada
mightymousetech Offline
mightymousetech  Offline

Joined: Apr 2017
Posts: 1,522
Ontario, Canada
Originally Posted by Dufus2
I used DOT 4 from Napa and it seems to be a little thicker, in very cold weather DOT 4 may be slower to respond. I just use the Walmart SuperTech DOT 3 brake fluid (paid $5 for a quart) and change it out every 2-3 years depending upon the condition. I just bought a brake fluid tester pen and my old fluid tested at 1-2% moisture after at least two years.


There is DOT 4 low viscosity. It is what BMWs call for.


Mighty Mouse Tech
BMW Tech, Former Acura Tech
2010 Civic Si Castrol 0W40, Redline MTL
2013 BMW 135i M Sport Edition Castrol 0W40, Redline MTL
Re: Is there any advantage to DOT3 over DOT4? [Re: spk2000] #4977211
01/12/19 05:35 PM
01/12/19 05:35 PM
Joined: Apr 2012
Posts: 6,345
MA
Wolf359 Offline
Wolf359  Offline

Joined: Apr 2012
Posts: 6,345
MA
Originally Posted by spk2000
Originally Posted by Audios
DOT 3 is less likely to absorb water and can usually go longer in the system before changing. However 4 is the better fluid.


Have heard this more than once but never saw anything that proves it is true and not just rumor. Anyone got some studies or evidence?


I heard that as well, further research seems to show that Dot 4 actually absorbs less water than even Dot 3 so that bit isn't even true. The more frequent flush recommendation may just be a good reason for some dealer to get the car in for maintenance.

Re: Is there any advantage to DOT3 over DOT4? [Re: littlehulkster] #4977266
01/12/19 06:46 PM
01/12/19 06:46 PM
Joined: Jan 2012
Posts: 289
Canada
nobb Offline
nobb  Offline

Joined: Jan 2012
Posts: 289
Canada
If you're changing your fluid often, the dry boiling point is more important. If you're not changing your fluid often, then the wet boiling point is more important. There's some DOT 3 fluids (like Ford PM-1-C) that actually outperform the DOT 4 standard for dry boiling point, but falls short in the wet boiling point.

Re: Is there any advantage to DOT3 over DOT4? [Re: Wolf359] #4977279
01/12/19 07:00 PM
01/12/19 07:00 PM
Joined: Dec 2009
Posts: 26,918
Regina, Saskatchewan, Canada
Garak Online content
Garak  Online Content

Joined: Dec 2009
Posts: 26,918
Regina, Saskatchewan, Canada
Originally Posted by Wolf359
I heard that as well, further research seems to show that Dot 4 actually absorbs less water than even Dot 3 so that bit isn't even true. The more frequent flush recommendation may just be a good reason for some dealer to get the car in for maintenance.

Something like Castrol LMA DOT 4 certainly markets based upon that aspect. Whether that's true for other DOT 4 varieties, I have no idea.


Plain, simple Garak.

2008 Infiniti G37 - Shell ROTELLA T6 Multi-Vehicle 5w-30, Wix 57356
1984 F-150 4.9L - Quaker State GB 10w-30, Wix 51515
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