If the smoke is white, it is engine coolant. You might notice the level dropping in the reservoir, or your mechanic might be filling it during other routine service such as an oil change. Coolant usually doesn't stop being burned in the engine while you're driving unless something different is happening. An example would be sitting in rush hour traffic on an unusually hot day. The engine would be hotter than normal and parts would expand and change shape more than normal. That could lead to something not sealing properly. Most of the time the coolant will continue to cause the smoke. It usually doesn't stop while you're driving.
Oil smoke is blue. Most commonly it will smoke right after starting the engine. Oil can run past valve guide seals into the engine where it collects. It is burned when the engine is started but it takes a lot longer to burn off than gasoline. Usually it will stop after a minute or two. This can be aggravated by a previous problem such as a leaky injector that allows excess raw fuel to get into the oil. That thins the oil making it easier to get past the piston rings into the cylinder where it will be burned. Over time, (weeks), the gas will be evaporated from the oil and burned and the smoking will stop.
Thursday, March 25th, 2010 AT 12:00 AM