I was driving home last night, and I noticed that I has some smoke from the tailpipe, as if the car was first started on a cold morning. However, the engine had been driven for 20 minutes on the highway prior to when I got home, and every other car that I have owned, the "cold smoke" stops once the car is warmed up. It is not blue smoke (oil), and there is no water in the tailpipe and the smoke is not "wet" (steamy) like it would be if I had a blown head gasket. The oil level and coolant level have remained the same over the past two days, as far as I can tell. It WAS pretty cold last night, around 32F. It was 61F today, and I have not noticed any visible smoke from the tailpipe today. Does this sound normal to anyone, or should I start checking plugs and gaskets and whatnot? I haven't pulled the plugs yet. Also, how can I tell if I am running synth oil or regular oil, and can the two be mixed if I need to add oil later?

Also, the engine starts and runs fine, no sputtering or hitching or anything.

 

It sounds normal to me. It could just be a weather related issue. New plugs wouldn't hurt though if they need to be changed...come to think of it, look at your plugs if you think something is up.

 

Like silvercoupe said it sounds normal with the temp. Also agreed that your plug could be a start to seeing whats going on. As for the oil yes you can mix the two they are compatible with each other. I wouldn't unless I had to but you can do it with no ill effects.