How long can I store an open jar of DOT hydraulic brake grease (e.g., SRAM or AVID)?
Background for question: DOT fluid is hydroscopic, i.e., it absorbs moisture from surrounding air and therefore keeping an open container for too long is not advised. What about the grease, though?
A long time. Assuming you can store the container well maybe the rest of your cycling life unless you go on a brake maintenance bender.
It’s silicon based grease that won’t dissolve in DOT fluid or destroy DOT compatible seals.
As others have mentioned, keeping it covered when not in use and storing it at a consistent temperature will greatly help keep free from contamination and stable.
One additional thing that you will see in grease is separation of the heavy/waxy components from the more liquid oils in a grease over time, even with care to keep it covered and at a stable temperature. This can occur even in unopened containers as well. This can be seen in grease from a squeeze tube when the initial material ejected from the tube is very runny and sometimes even clear. Discarding this initial material will usually yield a more consistent and expected consistency of the grease you are attempting to use. When I sense that grease has separated a little, I will attempt at mixing the grease to return it to a homogenous (consistent) form. If the grease is in a squeeze tube, I will try to move the grease around the tube as best I can, and if not successful enough, still just discard the initial material that is too runny to provide the protection needed by a thicker and stable grease.
Even with a little separation over time, grease is almost always still useable.
The grease will last for decades if not longer, provided its in a sealed container like a wide-mouth screwtop jar or a screw-mouthed squeezable toothpaste-like tube:
The small amount of air trapped inside the container won't noticeably affect the grease over time.
However this kind of cartridge needs to be installed into a grease-gun when it is opened. If you do that it will store as well as the jar and tube. If you leave these cartridges open to air with no airtight seal, they will attract dust and trap potential contaminants like bugs or swarf.
The one thing to do for preserving lubricants is keep them stable. Don't expose to heat cycles, keep them in the shade and out of the weather, and away from children.
