1986 chevy s 10 truck

I need help;My truck ran realy rough an was knowking put lucas hevy motor oil an went a way for a while an came back the other day turned off the truck an turned back on an white smoke started coming out the exhust any one know what i need to do to fix it thanks

White smoke is water being burned. This could be a head gasket failed and you coolant is getting in the cylinder or cylinders. That could be the reason why it was running rough to begin with.

Check the oil dipstick to see it the oil turns a milky white or cream color when you rub it between your fingers. If so,the water is in the oil. Have a trusted mechanic check the rest.