Thus, if you have to buy a replacement, select a plastic tank if it's available for your equipment. If you use fuel additives, be sure they are compatible with your fuel system. Keep in mind that manufacturers usually market these additives for automobiles. Read the label to see if it provides specific instructions regarding how much to add. If not, be sure to proportionally reduce the amount you add to account for the smaller tank size.
Oil is quite stable and has a long shelf life.
Therefore, storage doesn't usually affect its quality. The best advice I can give you is to stay with a known brand of oil instead of a generic type. One of the most common is gumming from varnish buildup. This will cause injector units to malfunction. No really good way exists to drain an injector unit completely, so the best prevention is to use chemical fuel additives for storage instead of trying to drain the system.