Until I was 49, I had nothing but bikes and motorcycles. IIRC, I used machine oil for cables.
I unboxed my new Radrunner three months ago. Right off the bat, it creaked when I squeezed the rear brake lever. It seemed to be coming from the lever pivot. Apparently it's coming from inside the cable a near the brake, where the cable takes a sharp bend. It seems the steel cable transmits the sound and vibration to the lever on the handlebar.
Nowadays, there seem to be lots of lubes just for bike cables. This cable is mounted differently from anything I've seen before. At the back end, the housing points somewhat upward, with no rubber boot or other protection.
I figured that without a boot, an oily cable would pull dirt into the housing each time I squeezed the lever. I tried silicone spray. It made no difference.
Do modern bike cables need lubrication? What's wrong with machine oil? Is there a way to protect the housing end with a boot? Is this a common Radrunner problem? Can it be fixed by rerouting the brake cable?