Brake Fluid
- bstig60
- Posts: 1141
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- Motorcycle: 2003 GL1800
2007 ST1300
1999 Virago XV1100LC (Sold 6/15/19)
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Brake Fluid
Will it hurt to mix synthetic Dot 4 with regular brake fluid in the GL1800 brake system?
Bill
- baumedagn
- Posts: 193
- Joined: Sat Oct 03, 2009 4:38 am
- Location: Lexington, SC
- Motorcycle: 2012
GL1800HPNM
Re: Brake Fluid
I don't know if it will hurt or not, but I would just flush out the old. Why take the chance?
- Viking
- Posts: 3708
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- Motorcycle: 2009 GL1800 AD
1987 Harley Softail Custom
1974 Harley FLH (sold)
1965 Harley FLHE (sold)
1957 Harley Chopper (sold)
Re: Brake Fluid
All Dot 4 brake fluid is synthetic, as are Dot 3 and Dot 5.1. The only petroleum based fluid is Dot 5. They say you can mix any of the synthetics together, such as 3 with 4 with 5.1, however, you will get an unpredictable boiling point. I would NOT do it tho. But 4 with 4 is just fine. It has also been said that you can clean out Dot 3 and replace with Dot 4, but you cannot clean out Dot 4 and replace it with Dot 3. (?????? why not if both are synthetic and can be mixed together) There is a lot of good and bad info on brake fluid to be found, but the mixing of Dot 4 with Dot 4 is not one of the bad ones.
- tamathumper
- Posts: 584
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- Motorcycle: 2003 GL1800A
Re: Brake Fluid
I just replaced all of my brake fluid with a big ol' bottle of "DOT 3+4".
So either I'm screwed, or it's from the future and it's actually DOT 7.
So either I'm screwed, or it's from the future and it's actually DOT 7.
'03 GL1800A - Warning: fopen() [function.fopen]: failed to open stream: Sense of humor not found on line 2
- Viking
- Posts: 3708
- Joined: Wed Sep 29, 2010 6:59 pm
- Location: North Bay, Ontario, Canada
- Motorcycle: 2009 GL1800 AD
1987 Harley Softail Custom
1974 Harley FLH (sold)
1965 Harley FLHE (sold)
1957 Harley Chopper (sold)
Re: Brake Fluid
It is from the future and can be used in place of either 3 or 4. It is likely Dot 4.tamathumper wrote: ↑Thu May 02, 2019 5:52 pm I just replaced all of my brake fluid with a big ol' bottle of "DOT 3+4".
So either I'm screwed, or it's from the future and it's actually DOT 7.
- keithg64
- Posts: 743
- Joined: Thu May 21, 2009 9:47 pm
- Location: Geneseo, IL
- Motorcycle: 2007 Gl1800HPNA Blue
2000 GL1500 Pearl Coranado Blue -sold
Re: Brake Fluid
Actually dot 3 & 4 & 5.1are all glycol based and the 3 & 4 I know are interchangeable. The dot 5 is synthetic and is not interchangeable with the others. The 5.1 is a glycol base with a higher heat range.
It's not what you buy, it's what you build.
- keithg64
- Posts: 743
- Joined: Thu May 21, 2009 9:47 pm
- Location: Geneseo, IL
- Motorcycle: 2007 Gl1800HPNA Blue
2000 GL1500 Pearl Coranado Blue -sold
Re: Brake Fluid
It's not what you buy, it's what you build.
- Viking
- Posts: 3708
- Joined: Wed Sep 29, 2010 6:59 pm
- Location: North Bay, Ontario, Canada
- Motorcycle: 2009 GL1800 AD
1987 Harley Softail Custom
1974 Harley FLH (sold)
1965 Harley FLHE (sold)
1957 Harley Chopper (sold)
Re: Brake Fluid
Actually "glycol based" does not mean they are not synthetic. It means they are synthesized from a glycol. Dot 5, in your link says Silicone based which is why it is not interchangeable with the other three. In my post above, where I stated that only Dot 5 is petroleum based, that also should have said SILICON based. Slip of the fingers before engaging brain.
