No need. The stuff is good for 30k miles. Keep the rest of it for the next time you need it.Winter is among us here in CT...waking up to ~20*F already, yay! I put half a bottle of dominator last winter, havn't lost any measurable amount of coolant (knock on wood). Would it be necessary or beneficial at all to put in the other half this winter? It's just sitting on the shelf currently.