I have a 10 speed bicycle I use for exercise. What do I lubricate the brake and gear cables with? ?

Question

I have noticed a light rust coating on them.

Answer 1

for slight sticking with cable use a silicon based oil.  For more major like rust use a water resistant grease.  But replacing them all together is the best idea.  It shouldn't cost more than $2 for the inner wire and $3 for the outer wire each.  And yes you can still buy them for older bikes.

Answer 2

Opinions will vary.  I use a very small amount of Tri-Flow on clean cables in sound condition.  A "coating" of rust would seem to call for cable replacement.  In addition, the cable housings may be contaminated; replace or at least flush them out (White Lightning's Clean Streak or WD-40).

Answer 3

Silicon based oil spray.

It's similar to WD-40 but WD-40 melts grease and hardens rubber (which is a bad thing).