2005 nissan frontier

With 170000 miles on the motor, it is starting to get a little tired and worn out. I had this same problem with a different vehicle. 183000 miles, blew smoke out the tail pipe, but still ran strong. Since it still ran strong, that tells us that the piston rings are still in good shape. I would have to say that with the head, either the valve guides, or valve seats are starting to get worn out, allowing small amounts of oil to pass into the combustion chamber, causing the smoke to come out of the tail pipe.