I have a 1994 Acura Integra with 209,000 miles. I have an hour drive to work one way about 50 miles so I put about 500 miles a week on it. I've had it about 6 months so far I had a Jeep Cherokee with 270,000 miles on it. I used Gtx synthetic 5w30 I think the first two changes but decided to try conventional this time last weekend. I noticed a little less gas mileage 32 instead of 33-35 and I also noticed a puff of white some in the morning. I thing I overfilled it by about a half quart though. That might have something to do with the smoke on cold starts. I use Mobile filters new every change 3-4000 miles. What oil should I be using for engine life and mileage?