Wash them down with mineral spirits (paint thinner) and with super fine 0000 steel wool.Dry them with a soft cloth and apply a coat of lemon oil with 0000 steel wool and let as much soak into the wood as possible. Then polish with a soft cloth. Make sure your pilot lights are off on your kitchen stove when you do this procedure, just in case. The paint thinner is very flammable, but virtually unmatched for it's grime removing properties.
Let me know how it goes! - Evette