Engine ice is ok to leave in for the winter. Supposed to flush it once a year. You could use 7th gear coolant which is the same stuff, plus an additive to make it a "lifetime coolant", comes in gallon sizes and is cheaper. I tried engine ice, regular coolant (honda) and dexcool and personally the dexcool seems to keep my temps down better. With engine ice I would overheat in heavy traffic...irritated me. No real # on the gauge but engine ice would normally run right on the midline. Dexcool and water runs a full needle or more blow the midline for me.