So, I've been using 5W20 in my 93 Vic with 180000+ miles. I've had it in for maybe 2 weeks, distance unknown due to defective odometer. In the short time I've been running the 5W20, I've already used 1 quart! And it seems the car is blowing more smoke than normal. Now here's my plan. Since I only changed the oil less than 1000 miles ago, the next time I need to top up, I'm putting in a quart of 15W40, and I'm going to continue to use a 15W40 whenever I need to add oil to the crankcase. Sure I <i>may</i> lose 2 percent off my fuel mileage, but I think it's worth the risk. What do you think?