it will seize up
If the engine was void of any oil it would seize in the matter of minutes and yes the car would not work.
the thick liquid would plug your radiator and ruin your water pump. and destroy your engine.
If your car's oil is changed on a regular basis at or around 3000 miles and you happen to miss that interval once in a while, nothing bad is going to happen. If you continuously are slow to get your car's oil changed, you can expect to cut you engine's life short.
Engine will overheat and seize
Have someone drain out the oil and replace the filter, now! Do not run the engine! This is not good for the engine!
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.
Excess engine wear at startup and at full operating temperature. Use only the weight oil that is recommended by the manufacture.
the oil lubricates the engine parts, without it the engine would lock up and be ruined
If you mean oil from a car? This would usually ONLY happen when there was a problem with the gasket between the cylinder head & the engine block. The oil will seep into the water cooling channels of the engine & leave a yellow whiteish scum in the water top up bottle on your car. Usually means a new head gasket on your car which will be quite expensive. Hope this helps?
Seized engine. Thousands of dollars to install rebuilt engine. Bad news.
what is a good engine oil to use in my car
If you drive your car without oil and it dies, your engine has seized. Time to replace the engine or the vehicle.