I have a 1994 Nissan Pathfinder that I've owned for over 10 years. It currently has 447,000km (275~k miles) on the original motor. But recently I've noticed on trips through hilly areas where I have to gear down and rev the motor high to maintain speed, it will use oil. Not a lot, but 1/2 to 1 quart every 1500km deepening on the load. I've gotten used to just slowing down and it is fine, just like my normal city driving. I know it's probably just wear, but I'm wondering if I should step up the oil viscosity? Still running the OE spec'd 5w30, usually Pennzoil. I do all my own work but I am by no means an oil expert. All gaskets have been replaced at some point and there are no leaks, so I don't think high mileage oil will help, right? And no I won't put lucas in it! lol