Blue/grey smoke is usually oil. White smoke is usually coolant in the exhaust. IE: blown head gasket or something. note: if the smoke goes away after it runs for a minute it's oil runnung down the valves when it sits. Common problem, won't hurt anything.
grey exhaust smoke is caused by your engine burning oil during the combustion process. this could be caused by a piston ring that doesnt properly seal, or another leak in your engine.
Burning oil
In most cases white smoke means you are burning gasoline inefficiently, black and gray are usually oil, however, that's the extent of my knowledge.
Could be a diesel? If not then replace your oxygen sensor on your exhaust. A bad oxygen sensor causes the exhaust smoke to be dark in color.
Sounds like you are getting coolant into a cylinder , is your coolant level dropping ? Could be a bad head gasket , warped or cracked head
White smoke means head gasket, cracked head or equivelant.
if it is white smoke engine need to rebuilt.
AnswerThere are several possible answers to what makes a car smoke. If the smoke is blue-black the engine is burning oil. This could be caused by worn rings or valve guides. If the smoke is gray black it is caused by a to rich gas mixture. This could be caused by a malfunctioning choke or injector, oxygen sensor, or other fuel related equipment. If the smoke is gray white it could be a blown head gasket or cracked block, allowing coolant to get into the exhaust system. Other causes of smoking could be an oil leak that is dripping on to the exhaust pipe or muffler.
White, water vapor. Gray/black unburned gasoline. Blueish, burning oil.
Piston rings or Rich oil .
Head gasket
It can be a number of things, but the most common problem is worn valve guides.