Mix Brake Fluids?
Thread Starter
Instructor
Joined: Jan 2022
Posts: 114
Likes: 14
From: Greenwell Springs, LA
Mix Brake Fluids?
Can synthetic DOT 3 brake fluid be mixed with regular DOT 3 in my 69 with PB? New master, calipers, pads and rubber hoses. Internet search yields conflicting answers. All seem to agree that brands can be mixed. I've got everything installed and used AC Delco 10-4110 for bleeding and initial fill. Seems as though I've not eliminated all air yet, and running low on new fluid. Haven't found AC Delco fluid locally. Haven't tried local GM dealers yet. I figure that source will be very costly.
Race Director
Joined: May 2006
Posts: 18,692
Likes: 2,572
Can synthetic DOT 3 brake fluid be mixed with regular DOT 3 in my 69 with PB? New master, calipers, pads and rubber hoses. Internet search yields conflicting answers. All seem to agree that brands can be mixed. I've got everything installed and used AC Delco 10-4110 for bleeding and initial fill. Seems as though I've not eliminated all air yet, and running low on new fluid. Haven't found AC Delco fluid locally. Haven't tried local GM dealers yet. I figure that source will be very costly.
Melting Slicks
Joined: Nov 2006
Posts: 3,393
Likes: 1,806
From: Apple Valley, MN
Unless you are going to track your car, DOT 3 is all you need.
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Race Director
Joined: May 2006
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Your original question was can you mix “synthetic” DOT 3 with “regular” DOT 3 and is misguided as there is no such thing as “”synthetic “ DOT 3. As the article states clearly, you can mix 3, 4 and 5.1 because they are all formulated from glycol ether base stock but you CANNOT mix any with DOT 5 which is silicone base.
Unless you are going to track your car, DOT 3 is all you need.
Unless you are going to track your car, DOT 3 is all you need.
https://www.oreillyauto.com/detail/c...ke+fluid&pos=0
Thread Starter
Instructor
Joined: Jan 2022
Posts: 114
Likes: 14
From: Greenwell Springs, LA
I read a comment elsewhere that all brake fluids are “synthetic.” There was no explanation, but I assume the writer meant that are man-made and not “found in the wild.” I’ve purchased some DOT 3 synthetic and will struggle forward. Bleeding is my least favorite car related chore.
Melting Slicks
Joined: Nov 2006
Posts: 3,393
Likes: 1,806
From: Apple Valley, MN
Most of us on this forum are “boomers” and spent our formative years in a time when DOT 5 silicone brake fluid was not commercially available. As a result, we never had to differentiate between “synthetic” and “non-synthetic” when it came to brake fluid until DOT 5 emerged in the early 70s.
Technically speaking, since the term “synthetic” indicates a man-made product, any DOT 3, DOT 4, DOT 5 and DOT 5.1 fluid is synthetic. Adding the term “synthetic” to the label in this case is a marketing tactic, designed to promote the product. If I were the CMO, I’d have chosen “enhanced” or something similar.
Apologies if my frame of reference is rooted in the 60s but at the end of the day, you can’t mix a silicone based DOT 5 with any glycol ether based fluid, irrespective of the number.
Technically speaking, since the term “synthetic” indicates a man-made product, any DOT 3, DOT 4, DOT 5 and DOT 5.1 fluid is synthetic. Adding the term “synthetic” to the label in this case is a marketing tactic, designed to promote the product. If I were the CMO, I’d have chosen “enhanced” or something similar.
Apologies if my frame of reference is rooted in the 60s but at the end of the day, you can’t mix a silicone based DOT 5 with any glycol ether based fluid, irrespective of the number.
Thread Starter
Instructor
Joined: Jan 2022
Posts: 114
Likes: 14
From: Greenwell Springs, LA
No apology needed for this boomer. I’m the original owner of this 69 and it’s my only Vette. Thanks to the original lip seal calipers I’ve purchased much brake fluid (and repair kits) over the years. Never encountered this “synthetic” issue before because the car sat idle for many years (my bad). The new calipers I referenced at the start of this post are o-ring so they should be the last…if I can get the system bled properly.
Struggling by myself with a MityVac but can’t seem to get a good seal at the bleeder screws. I’ve even tried using brake grease around the screw threads but still getting lots of bubbles. Don’t know if these are from around the threads or still coming out of the system. #@&%
Thanks 69L88 for your feedback.
Struggling by myself with a MityVac but can’t seem to get a good seal at the bleeder screws. I’ve even tried using brake grease around the screw threads but still getting lots of bubbles. Don’t know if these are from around the threads or still coming out of the system. #@&%
Thanks 69L88 for your feedback.
Race Director
Joined: Feb 2001
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From: Grapevine Tx
2018 C3 of Year Finalist
2016 C3 of the Year Finalist
No apology needed for this boomer. I’m the original owner of this 69 and it’s my only Vette. Thanks to the original lip seal calipers I’ve purchased much brake fluid (and repair kits) over the years. Never encountered this “synthetic” issue before because the car sat idle for many years (my bad). The new calipers I referenced at the start of this post are o-ring so they should be the last…if I can get the system bled properly.
Struggling by myself with a MityVac but can’t seem to get a good seal at the bleeder screws. I’ve even tried using brake grease around the screw threads but still getting lots of bubbles. Don’t know if these are from around the threads or still coming out of the system. #@&%
Thanks 69L88 for your feedback.
Struggling by myself with a MityVac but can’t seem to get a good seal at the bleeder screws. I’ve even tried using brake grease around the screw threads but still getting lots of bubbles. Don’t know if these are from around the threads or still coming out of the system. #@&%
Thanks 69L88 for your feedback.
Le Mans Master
Joined: Aug 2017
Posts: 8,336
Likes: 2,809
From: Cool Northern Michigan
MtCarl,
Yes, its deceiving if the bubbles have truly come from the brake-lines or not.
I just "barely" crack open the bleeder. I know it takes longer to vacuum, but the more threads in the caliper hole the better.
And some of us have noticed an odd manufacturing defect in some bleeder screws: Too sloppy.
I wanted at least 6 bleeders, ended up going to four different name brand stores. Nobody had the size needed, in stock.
Out of the 8, I finally bought, only 3 fit correctly. The rest appeared "undersized".
You can always use vac to get things moving then let gravity finish the job.
Or see if EBay has a used Motive Pressure Tank.
Yes, its deceiving if the bubbles have truly come from the brake-lines or not.
I just "barely" crack open the bleeder. I know it takes longer to vacuum, but the more threads in the caliper hole the better.
And some of us have noticed an odd manufacturing defect in some bleeder screws: Too sloppy.
I wanted at least 6 bleeders, ended up going to four different name brand stores. Nobody had the size needed, in stock.
Out of the 8, I finally bought, only 3 fit correctly. The rest appeared "undersized".
You can always use vac to get things moving then let gravity finish the job.
Or see if EBay has a used Motive Pressure Tank.
1967 Pedal Car Champion
Joined: Mar 2020
Posts: 9,030
Likes: 4,175
From: US-PNW
Actually to my surprise also there does exist synthetic DOT 3
https://www.oreillyauto.com/detail/c...ke+fluid&pos=0
https://www.oreillyauto.com/detail/c...ke+fluid&pos=0
