My brake lines had a lot of old rusty, gelatinous goo for brake fluid (Car sat for 14 years). I have cleared all the lines, wheel cylinders, etc. but have not changed the lines. Rebuilt calipers, wheel cylinders and new master cylinder are in place. My question is: what type brake fluid should I use to get more use out of my old lines? Assuming there is some rust internally, would silicone be a better choice since it does not absorb moisture or would DOT 3/4 suffice if I changed it out each year?

Mike

DOT 3/4 is fine for a street driven car.

I'll second Mr. Coffey.

DOT 5 is not all that it is cracked up to be. Absorbing moisture (as DOT 3/4 does) is a good thing. With DOT 5, if any moisture does get into the system it simply migrates to the lowest points in the system (calipers and wheel cylinders) and sits until it gets flushed out. Generally, it causes rust and corrosion there before that happens. DOT 3/4 holds the moisture in suspension instead.

I have used DOT 5 in special cases - notably on off-road bikes and ATVs where I'd change it very frequently. But I won't use it in a street car.