I'm not sure, for the cost of two or three gallons of RV antifreeze, that it's worth taking a chance that the stuff hasn't lost strength or become contaminated from year to year. I think we used about 3 gallons in our RV last fall, at about $3 (?) a gallon, as bestI can remember. Of course, I haven't gotten the trailer out of storage yet for the season, and I may wish I'd filled the trailer from floor to ceiling with antifreeze.