If it was white smoke and your coolant was leaking, then the smoke was from your coolant. If your leaking oil slow enought to burn off and not leave stains or a trail then its probably coming from a gasket somewhere, if you engine is dirty (im sure it is) look around everywhere metal meets, if the is a clean spot that looks like its coming from somewhere thats gasketed, then thats most likeley where the oil is coming from because motor oil contains detergents, same would go if you tranny was leaking, just look for a clean spot. If you find somewhere like that, or you otherwise discover the leak, just replace the gasket. How does you car start in the morning and after you drove it for a while? If it starts cool in the morning or first time you drive it, but struggles or doesnt start at all when the engines warm then you may have a blown head gasket, which is replaceable but a pain in the ass most of the time. If it starts cool all the time, and doesnt knock or lose compression then you just got a leak somewhere, find it, fix it, have a good day. lol.