I've never been a fan of biodiesel. The stuff is too corrosive which can eat up older trucks rubber lines and seals not compatible, and it gels easier than normal #2 in colder weather. Unfortunately there are stations which only offer bio blend diesel, but I understand that the ratio of bio is minimal. Knowing that algae is probably the biggest issue with older diesel, using some fungicidal protectant and full tanks should be all one needs. And if you dont plan on starting or moving a vehicle for over 6 months then there are far more things to be concerned with besides fuel.