My sister's ride is a '02 Toyota Highlander with 1MZ-FE V6 engine. The vehicle is not driven hard, does not puff smoke on start-up, does not leak oil but every time I check the oil level it needs more (M1 5-30, factory spec weight). I wish I could tell you it uses x amount of oil in x miles but I don't have those figures. Each time I check the dip stick (at least every other week) I need to add at least 1/2 quart. I thought maybe the rings were frozen so I added Rislone Engine Oil Treatment but so far there has been no improvement in the oil consumption. Any suggestions where I should look or what I should do next will be appreciated.