I've done the search deal, and of course read a lot in books, but I can never seem to get the smoke deal straight, especially when it comes to plain ol' gray/white smoke. In understand why it's there on a cold start-up in a diesel, but what I'm wondering is why so many cars (both gas and diesel) emit whitish smoke during cold weather while their simply driving around. I realize this could be the world's dumbest question, but anyone who's familiar with me knows I'm not afraid to ask those. I see tons of vehicles with a little waft of white behind them in the fall/winter months, and I suspect my car has something similar ... I can never see it behind me, but sometimes when idling in traffic at night I can see it in the headlights behind me. Yet during the day I can stand behind my tailpipe and NOTHING is coming out (well, nothing visable). Why can I sometimes see this on winter nights? Is it a product of emissions interacting with cold air? What's the difference between "normal" smoke, smoke from unburnt fuel and smoke from a crack head? I can't imagine every car I see with a little waft of smoke behind it has something catestrophically wrong with it, so I suspect there's something obvious I'm missing. Anyone want to give me White Smoke 101?

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1987 300D, arctic white/palomino--314,000 miles
1978 240D 4-speed, Euro Delivery, light ivory/bamboo--370,000 miles
2005 Jeep Liberty CRD Limited, light khaki/slate--140,000 miles
2018 Chevy Cruze diesel, 6-speed manual, satin steel metallic/kalahari--19,000 miles
1982 Peugeot 505 diesel, 4-speed manual, blue/blue, 130,000 miles
1995 S320, black/parchment--34,000 miles (Dad's car)

the whole lil puffs of white smoke in cold weather is water vapour condensing in the colder air that was in the exhaust.. IIRC

at night my car smokes heavily at take off with WOT... i love doing it then before it shifts i let off then stomp on it to let out a really big puff.. just to screw with the jerk in the bmw.(im actually under speed limit while doing this.. i dont do it much often) but on the highway going WOT for long periods of time do good on a diesel

Normal smoke is a gray/white smoke that is just the byproducts of combustion and includes some soot. In the cold weather, the water vapor, also a byproduct of combustion, appears as "white smoke".

Smoke from unburnt fuel can be white smoke if the fuel doesn't combust properly due to low compression or poor atomization. It can also be black smoke if it combusts incompletely due to insufficient air.

Smoke from a crackhead has a distinctive pungent aroma that can be noticed by anyone within 20 feet of the crackhead. One may also notice the crackhead doing some strange behaviors while smoke is being emitted.

Simply brilliant.

Also if you happen to have a cracked head and/or bad gasket, you may smell a sweetish odor, the smoke will be predominately white, and you are in a workd of hurt.

Reminds me of a time when I was drag racing a camero and his head blew. Two tailpipes of thick fog and as I drove through it I could only think "this can not be good for my lungs". In fact I felt rather punky for the next few days. Won the race though...
-nB

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'83 300D Turbo
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