Should I leave (anti-freeze coolant) in radiator during winter storage? Hasn't been changed for several years and don't use much.
I would replace with fresh 50/50 or what your temp gets down to, start and run (if it does). If it does not run I would ether use the premix or mix before putting in it will not mix on it's own. While the old stuff "MIGHT" be ok, just sitting may have lost it protective ability. Good time to do a quick flush also.
Change the coolant every three to five years and replace with 50/50 mixture.
Also, if you already don't own one, spend a few dollars and get an antifreeze coolant tester from the auto parts store and check the freeze point before putting the car up for the winter.
I have both the arrow style below and the tube and bead style. I prefer the arrow style.
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