+1 on Renaissance wax, it's used by museums so should not discolor or harm any items, I use it in some non-stainless blades I keep on display, it keeps rust from forming also brass from tarnishing. The tin I bought will last me for many years, good investment.
For a car blade I think the heat/cold changes would affect the horn more than the steel of that knife.
For a car blade I think the heat/cold changes would affect the horn more than the steel of that knife.