there are several things that keep the engine. some key ones are fuel, electrical (ignition), and compression. but the most important one of all is the flywheel. flywheel is chief.
Worn out piston rings [or the cylinders themselves] and valve seating are the typical culprits.
You can use a heavier weight oil, 20W50 for instance, to try and slow the amount of oil consumed, but...
Usually caused by lack of oil changes or operation of the engine with under less than ideal conditions like: Short runs that do not warm engine completely Poor quality engine oil Engine has something...