Re: Oil useage
If it's not leaking on the ground, you may be approaching ICE repairs. Our 2002 Prius still goes 5k to 7.5k between oil changes with no noticeable loss of oil. However, we only have about 115k miles on it.
If the ICE is burning the oil, it means that either the valves/valve guides or piston rings are letting the oil get into the combustion chamber. A quick way to check is to run your finger inside the exhaust pipe (before it gets hot from the ICE running). When burning progresses, you'll see a significant increase in black oil soot coating the inside of the exhaust pipe. In severe cases, it'll be wet oil residue (actual oil, not liquid water).
Of course, the best way to check is to have the cylinder compression checked. This isn't difficult, although it may seem daunting if you have no engine repair experience. It shouldn't be too much at the dealer, although everything is relatively expensive there. However, it seems really low mileage for ICE problems, unless your vehicle has been abused or in an accident that my have caused related problems.
I don't think I remember anyone ever overhauling an ICE on this site. With the electric motor sharing the load, I would expect that the ICE would last significantly longer than in a regular automobile. And, Toyota engines usually run a long, long time before needing a valve job or engine overhaul, typically 250k+ (assuming normal driving conditions/habits and routine maintenance was done regularly). Therefore, I would expect the ICE to last quite a bit longer than the mileage you have on your car.
Let us know what you find after checking the compression and the exhaust pipe.