I filled my 2017 L3901 two years ago completely full and added a full can of Seafoam. I only used it about 1.5 hours in the past 2 years until last week when I shredded at my deer lease for 3 hours. I still have a little less than 3/4 of a tank of diesel from 2 years ago. The tractor ran great and no water in the fuel separator. Would I be better off syphoning out some of the old diesel and refilling or just top it off with fresh diesel and a more seafoam. I don`t want the tank to be less than full over the winter to prevent condensation.