The engine has been running low on oil and i've been out of town and let someone use it.they said that when they drove it it would run a kittle hot but when i checked the coolant level it was fine .Needless to sasy they didn't check the oil level and when i got it back i put two quarts of oil in it.I guess that wasn't enough .Right after i put in the oil about 50 feet later there was a constant cloud of white smoke coming from the exhaust.It is now full of oil but still the heavy smoke and the coolant level is still good.What should i check for and possible need to replace?