I admit i'm not very mechanically inclined, so please bear with me. I need to add about a 1/2 quart of oil to my 1.8t. I'm going to add some 10-30w dino. If i only use half of the container, can i save the other half for later/or is it once the container is open, it's considered "contaminated"?? Is 10-30 ok to use (ny area)?? My mileage is 1700 miles. Thanks


Al
99.5 1.8tqtsc