White smoke coming from your tail pipe in the winter is normal when it only lasts for a few minutes. This is usually from water in the exhaust turning to steam. If it continues, check for an antifreeze leak into the engine. Blue smoke normally means your car is burning oil. If this only occurs at start-up, the condition may not be serious. Excess smoke is an indication of a major problem. Black smoke is an indication of a too rich fuel mixture or a problem in the injection system. Light grey smoke may mean transmission fluid is leaking into the system.