why does my 2001 astro burn oil? no leaks

The reason oil burns is that it escapes from where it is supposed to be. As a car ages, different parts can become worn and not provide a tight seal around the oil. The oil leaks out and touches the hot components on the engine. The worst case scenario is that your piston rings are worn. More oil is left behind in the combustion chamber where it’s burnt. However, this doesn’t usually happen with newer vehicles under 100,000 miles. Another possible cause are leaking valve seals. They normally prevent oil from running into the combustion chamber. When they begin to wear out, small amounts of smoke come out of the exhaust when the engine is started. When a PCV valve is worn, it also allows oil to seep into the combustion chamber. A defective or worn out PCV valve allows pressure to build up, which pushes out gaskets that are designed to seal out oil. A correctly working valve removes gases from the crankcase to prevent the pressure buildup.

It could be from engine wear due to high miles. Piston oil control rings may not be doing their job anymore or the valve guide seals may be worn out. Do you have blue smoke in the exhaust?