It is either leaking out, or blowing by the spark plugs and being burned up. You should be able to determine which, although oil leaks that only occur at high temperatures might elude discovery.
If the engine was void of any oil it would seize in the matter of minutes and yes the car would not work.
An oil leak is always going to be out of the engine as the engine contains oil and the car does not. I think you are saying you are loosing oil with no apparent leak. If that is the case the engine is burning oil and that is why you see no leaks.
the oil lubricates the engine parts, without it the engine would lock up and be ruined
it will seize up
what is a good engine oil to use in my car
Synovial fluid is the fluid that lubricates joints in the body so it would be similar to the oil of a car engine.
If you drive your car without oil and it dies, your engine has seized. Time to replace the engine or the vehicle.
Nothing provided the engine is not started up. With no oil, a running engine would eventually seize up.
If your car makes a knocking notice referred to as "engine knock" then you left your engine on low oil for too long and your engine is now toast. It's like you had a piece of sandpaper rubbing a nice table with a clear coat. If you don't maintain the clear coat the paper will eat the wood.
If you run too low on oil in any car, the engine will freeze up and be ruined. The whole engine would have to be rebuilt or replaced which would cost over $3000.00. Better get a quart or two of oil. Much cheaper than a new engine and a car that will probably never be the same again.
The engine oil capacity in a 289 CID in a Ford passenger car would be 5 qts with oil filter change.
You would need to tell me which car you have. Please update the question, or ask a new one.