Purchase Brake Fluid in Gallons?

Joined
Aug 30, 2004
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Generally accepted best practice is to use brake fluid from a new, sealed container for every brake fluid service.

However, if you purchase DOT3 brake fluid in gallon jugs and plan to use all of it within a few weeks, is there any downside to this approach? This fluid will still be newer than the fluid in the vehicle being serviced.

Obviously the container will remain capped and will be stored in a dry area.
 
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I am due for new calipers on my F-350 , the Cherokee needs a new metal line and I'd like to do a brake fluid flush on the Grand Marquis. Will definitely buy a gallon for when that time comes.
 
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I average 2 quarts a months so it would depend on how much cheaper by the gallon. But trying to fill the master cylinder from a gallon container is going to make a mess.
 
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I no longer flush my own brakes. For one thing they don't need it as often since I moved to the desert. (Moisture in brake fluid and engine crankcases out here is a rarity).

And another is I'm getting too old to be crawling around so much underneath my vehicles. A quart of brake fluid will more than likely last me the rest of my life. But if I had a need for more, I wouldn't hesitate to buy a large volume jug.
 
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I saw a gallon jug of Prestone DOT 3 while I was recently in the local Autozone. It caught me by surprise, as I don't think I've ever seen brake fluid in a gallon container before.

For me, it would be a no. I can do a good brake fluid flush with a quart, and have some to spare, on both of my cars. Also, since there are some very good DOT4, and even DOT 5.1 offerings on the market for fair prices, I prefer to go with these. So DOT3 gallon is off the table.

But if I was a flat lander, and had more vehicles, I wouldn't have a problem with buying DOT3 in a gallon.
 
Joined
Jun 15, 2003
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ME
I buy it by the gallon and it lasts a few years. The bottle doesn't breathe much if any, especially compared to a vented master cylinder reservoir that gets heat cycled.

Your proposed use is more than fine. The "new bottle everytime" is paranoia.
 

JHZR2

Staff member
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Dec 14, 2002
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New Jersey
If it’s a few weeks I see no issue with it. If you want to be even more careful with it, get a can of bloxygen and inert the headspace in the bottle. Overkill for sure, but an option…
 
Joined
Jul 13, 2003
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Tracy, CA
I only buy in quart containers when I'm using the bleeder ball to flush/bleed. For top-offs, I buy the little bottles.

I read someplace that reasoned that large containers with large air space will absorb moisture. Genius me, I figured I spray canned air duster air over my left overs before quickly capping to preclude moisture. The result is the container you see to the left.
 
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May 6, 2005
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I'm hearing a typical open shelf life recommendation is 12 months, but it needs to be tightly sealed. When sealed it may be indefinite. However, I've got some Motul DOT 5.1 fluid where they claim that they've purged the empty space with nitrogen. Not sure what that would do.
 
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