Hi there, i have a few z50 wich I won’t be using anytime soon. Im planing to remove the original tanks for storage and wen ever I want to ride them just use a few aftermarket tanks I purchased. Tanks presently have some gas, im going to empty them. How is the best way to store them to avoid rust? Put Any oil inside? Brand? Viscosity? Best oil to be used? Should i clean them for any gas residual? Product? Suggestions please.