I've used RIG, FP-10, 3 in 1 oil, CorrosionX, Renwax, and Eezox to keep rust away from my carbon steel blades. Not all at the same time of course. Of bigger importance than the actual product used, is the maintenance schedule itself. If you don't take pride in your tools, the tools will likely suffer. Cheap stainless knives sell in high volume because most folks are more worried about discoloration or rust than they are about edge retention and cutting/sharpening ability. Not too many years ago that wouldn't have been the case.