[Boatanchors] Should dummy load oil ever need to be changed?

[Ed H]

I have a cantenna that is 35+ years old. It hasn't been used lately. It seems to be a little less full than it was when bought new. I purchased the oil from the Heathkit store as well. I assume the oil is simple mineral oil as it was clear and approximately 10 to 20 weight viscosity. I used it moderately for 1kw+ tune up for 20 years before I put it in storage. Now I plan to use it for 150 to 1kw AM and cw tune up and testing. Should I change the oil?
Ed-kv5i