My Civic seems to use quite a large amount of oil. When I get on it there seems to be a grayish/blackish plume of smoke that comes out the back. It's not a huge plume of smoke, but it is more than should be. It burns about 1 quart of oil every 350 miles. I was running Penzzoil 5W-30. My local Honda tuner guy told me to try 10W-40. It doesn't seem to have made much of a difference. The car is a completely stock D15B7. I've tried varying my driving styles but it seems to use the same amount of oil no matter how I drive it. If anyone has any comments/insights/solutions, I would appreciate it very much.