High Mileage Prius 2007 Engine Problem

When the oil got low enough to trigger the warning, some damage to the engine resulted. That warning is intended to let you know the engine is close to failure. (All cars, especially aging ones, should have the dipstick checked regularly.) It may be time to think about another engine.

Since we didn't see the spark plugs, we don't know the failure mode. Spark plug failure could indicate severe engine problems, or maybe just spark plug failure--they may have been original plugs.

Fuel injectors should not be "cans of worms." They can be replaced.

If the mass air flow sensor (MAF) has never been cleaned, that could result in poor performance. Same with the PCV valve.

 

What Andrew said. He's right about engine damage don't put any more money into this motor. Almost always when you run the oil so low it throws a check engine light the motor is damaged. It destroys the engine lower end bearings. That whole area is splash lubricated. No oil no splash.
Its important to keep the oil at the full line at all times........on all cars.

Be aware lower bearing engine damage will sometimes start out and show as a misfire due to lower end vibration which disturbs the cam/crank sensor readings. Be suspicious of this if the misfire codes bounce around mysteriously.

Btw, changing 3 out of 4 plugs is pretty nutty. At the very least you want to pull ALL the plugs out and check ALL the ignitors (cops-coil on plug) to inspect the cop boot. A bad cop boot will throw a misfire cel everytime. So your dealer is very expensive and not to good.

if you are forced to take this car to the dealer every time it starts doing something you will soon be broke. You need to find a decent mechanic.

Unfortunately a used high mileage Prius is sometimes a bad choice if you have no car repair skills or a solid mechanic who will not rape you every time the car is not running good. What little you save on gas will go right out the window on the dealer repair rack. My dealer here is $140 an hour. A Corrolla is a much better choice.