A family member has got a 2002 Toyota highlander with the 3.0 V6. When I saw it last I noticed it was low on oil, like real low, not even on the dipstick. At this point she was about 6 months and 4000km into her last oil change. She religiously follows the oil change sticker, and was about to get one anyways, so I offered to do it for her. I drained just over a liter of oil out of her pan, the car takes about 5. What could be causing such high consumption? The car has 250k km. Doesn't really smoke. Looks very dry from underneath and is not leaking. I checked the pcv valve and it seems to be operating properly. She has receipts from the previous owner, so I know that the engine was well maintained. Oil changes were done on time, and all but three were done at a Toyota dealership (including the one I did). The dealer has never told her that they barely got any oil out of it. I know this engine has a history of sludging, but given the service history, I imagine that wouldn't be a problem. However, isn't unlikely if the engine is running on small quantities of oil. Anybody familiar with the engine have any recommendations on what we should do? Would It be a good idea to start running a high mileage synthetic? I put in some Motomaster 5w30, in case anyone is wondering.