The problem with stale gasoline is the alcohol that might be added to your gasoline, typically at 10%, does not evaporate as much as the light petroleum fractions do. Consequently the alcohol content in stale gasoline can be significantly higher. So, I recommend not using stale gasoline over 10%. Otherwise seals, such as BUNA n and silicon seals, can be ruined by excessive gasoline content. For these seals I have found the alcohol content must be at or below 3%.
More importantly not all of WVO will dissolve into petroleum distillates, so it is necessary to allow for a settling period of about 2 weeks for WVO, and a means of draining the sediments out of the blending tank, such as having a drain valve on it, as well as a cone, or dome-shaped bottom to the blending tank.
I have not had the problem of WVO dissolving, or rusting the fuel tank; however, my deuce tank is definitely galvanized, which attracts high melting point triglycerides and gum out of the WVO, which coats the tank. The good news is the high melting point triglycerides and gum make an impermiable barrier to water.
As mentioned above your problem with WVO-based fuels is the waxes, gum and HMPTs are going to precipitate out of solution, so you have to remove it, or otherwise your fuel tank will get sludged up in no time.