It does not take very much oil to make smoke. Synthetic oil does have some detergent qualities and if you just changed to synthetic you might have loosened up some varnish and stuff that was sealing around the valve stems and now it is leaking a little. I would say if, under normal driving you do not see smoke then just forget it happened. I think though, if you look closely you will see smoke now - especially if you look out the back at night with headlights from behind. Still, if the car runs OK and the smoke is minimal it probably won't do any harm to just keep driving it.

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Marty D.

2013 C300 4Matic
1984 BMW 733i
2013 Lincoln MKz