#1 cause of oil consumption is bad valve stem seals. You 'can' replace the stem seals without removing the heads but I would consider giving the heads a once over (hot tank, pressure test, check for valve run out and lap the valves if everything checks ok) An oil flush will help with hydraulic noise but while it's siphoning oil through the valve stem seals it's going to run like a dog (oil consumption, lots of smoke, loss of power)