Smoke

Excessive unburned fuel causes black smoke. White smoke is a sign of burning engine coolant. That is caused by a leaking cylinder head gasket. You will see the level dropping in the coolant reservoir. You can verify that further by adding a small bottle of dark purple dye to the reservoir, then you check a few days later with a black light. The dye will show up as a bright yellow stain that you follow back to the source. If the head gasket is leaking you'll find the dye inside the tail pipe.