Let's assume I have a car with 30k miles whose service manual does not specify any interval for changing brake fluid, and the fluid is still transparent with no visible contaminants.
Is it feasible for me to use a turkey baster to suck out 75% of the fluid in the master cylinder reservoir, replace the extracted fluid with the same amount of new brake fluid, then repeat that process every so many miles miles until a satisfactory number of cycles are complete, effectively replacing most of the fluid in the system? If so, every how many miles should I do the partial replacement, and for how many cycles?
The idea is that as the brakes are used over those miles, the fluid is mixed and routed through the entire system. That mix is then diluted of old fluid even further when the process is repeated again. After enough cycles, the old fluid (along with its contaminants) would be diluted so much that it is effectively clean and has a low enough contaminant concentration to be satisfactory.
I chose 75% for the amount to be replaced because I didn't want to suck the reservoir dry and possibly introduce air into the system, which would make it necessary for me to bleed the brake system. That's what I'm trying to avoid having to do.
The one thing I can think of that could thwart this idea is that the fluid in the master cylinder reservoir doesn't completely cycle through the system in any reasonable number of miles (or ever). Is my idea a valid one, or am I mislead?