Be careful using oil on a potentiometer. I have seen some pots where oil has loosened the binder holding the carbon to its surface and ruined it. In addition oil works wonderfully to capture contamination causing future problems.
This is why control cleaners are manufactured specifically for cleaning & lubricating pots & switches. The lubricants contained in these products are formulated not to cause additional problems. WD40 and solvents of an aggressive nature are not made for electronic applications such as this.
