I've got a 6th gen, 4 cyl. and it does the same thing when its cold but it all goes away when it warms up. no biggie, i've heard they all do this. i used mobile one synthetic as well (5-30) as well. i heard some mention before that when you take your car back for a service at the dealer, like usuallly the 30k service, they adjust your valves. but i heard its normal. mine only has 42k on it. im not really worried about it.