In the early mornings when it is cold my front locker light flashes on the dash for the first 1-2 miles of driving. This occurs when the overnight temps get aron 35-40 degrees. Today, on the way home I was somehow able to get to about 80 mph with my minivan motor and it began to flash again. Any ideas. I am going to drain and change the oil with synthetic but thought I would also check with you all before I do so, what wieght would you recomend?