help me oil

[4runna1]

HI my 1st gen 2.4D is using a rediculose amount of oil i preety much have to top it up every week. . When i rev the engine it puts out black smoke and leaves a watery black mark on the ground. Only if i rev it hard, it doesn't smoke when i drive it normaly. it also smokes when i go offroad up a steep hill ect.
Does any one know what it could be. Ive already taken it to my toyota specilsed they checked the piston rings and they fine. its not leaking a considerable amount where i can see

 

[wolfgang]

Not many diesels in the US at all. If it were gas I'd say its the valve stem seals, valve guides, valves and finally the piston rings (after doing a compression check) --- heck, old Diesels always left in a cloud of smoke! Not sure how one would check piston rings other than by low compression reading (could just be one cylinder too) or a complete tear down.