oily deposit on the spark plugs electrodes
You can tell this before an oil change. If you see blue smoke coming out the exhaust your engine is burning oil. If you're oil level is low and you have no oil leak your burning oil.
spark plugs fouled with oil. blue smoke from tail pipe.
Yes. Blue.
The engine is burning oil
You're burning oil.
It is either leaking it out or burning it.
your car has oil burning in the combustion chamber of your engine , need to rectify the engine block and replace piston rings
The engine is burning oil.
When you run your car low on oil you increase the instance of burning your motor. If your motor burned out your car won't work.
Sounds like you've got burning oil, probably due to a leak.
If it has no visible leaks and you are loosing oil, then it must be burning it. Remove the hose from the PCV valve and see if there is oil in it. If so you will need to be sure that it is venting.
white smoke is a indication of oil by passing the piston rings and entering the combustion chamber (Your burning oil). Not unusual for a older car especially when the car has been sitting for awhile. If it continues after warm up, you need a engine rebuild or a new car. Check a auto supply store, they have oil additives that reduce the oil burning.