My gt has gotten Mobil1 since around 40k miles. With over 222k miles now, the valve seals are a little tired. I get the tell tale puff of smoke leaving a long stop light or on a hot start after sitting a bit, and it is worse in the summer. I have heard synthetics, and particularly Mobil1 find any leak worse than other oils. Do you think a conventional would give me less of a smoke show? It doesn't consume a lot of oil, maybe a quart every 1500 to 2000 miles, but it is a bit embarrassing to leave the smoke.