565bbchevy brought up the best point of all. Compression fittings are designed for indoor plumbing. That means the alloys used are not expected to be subjected to road salt or other chemicals, like brake fluid. My guess is that any car that needs a brake line spliced is on it's last legs anyway and the next big buck problem will be the last straw. They probably don't last long enough to corrode and fail. Now, a car that is being restored or hot rodded is a different story. It will be used for a long time, and probably be overpowered too. That car had better have the best brakes money can buy. I personally buy big bulk rolls of brake line from places like Northern Auto and use my double flare tool to make what I need. Strive for one piece lines. But places where you can't get access because the factory put the brake lines on before the body, you need a union.
