I Have a 97 nissan altima. i went on a summer vacation for 2 months. came back....changed the oil and put coolant in. I noticed when i drove that white smoke came out of the exhaust. granted i dont drive the car that much....everytime i do white smoke comes out every once in a while.....its been more than a week. after about 10 mins....it blows out white smoke. can it be the oil? how much oil are you suppose to put in. just worried. car has 103,000 miles

thanks a lot