The plastic knob on my cooker's top oven/grill has broken off?

The plastic knob on my cooker's top oven/grill has broken off, leaving just the steel rod going in to the cooker front. This is very stiff even to turn with pliers. I plan to order a new knob, but am wondering whether the rod itself can be oiled to make it easier to turn when the new knob arrives.
Knobs have split and broken several times over the 10 years+ I have had the cooker (a Cannon Camberley) - I think these plastic things are too weak for their purpose and are a design fault. I'm not sure spares for this model are still available!