After my trip to Syracuse, NY and putting all together 815 miles I've noticed that I have to add about 12-14 OZ of oil. What is particularly intewresting is that on my way to Syracuse engine did not take any oil - I've checked level right after the arrival. So all the oil was "taken" on my way back. I've read that Isuzu engines are "taking" oil so my question is 12-14 OZ per 800 mile is OK or excessive and does the oil brand/viscocity has anything to do with it. I am using Synthetic Blend Quaker State 4X4 10W30. Where oils is going ? I have no black marks on the ex pipe, no leaks... does it evaporate on 80 mile per hour speed ?