Been changing oil on cars since 1968... I know what I am doing... bought a program 2007 HHR in 2008... it is now approaching 200,000 miles... I am the only one that has changed oil on the thing all these years.... replaced one rounded drain plug and bought a new cap for the oil filter about five years ago.... computer said 30% oil life left this morning but I like to change it more often and had another vehicle in the garage so why not.... Did the usual.. ramps... drain plug and knew right away I was in trouble as the oil came out at a very slow rate.... and I was right.... not quite three quarts.... but the red idiot light never came on in the last month or so.... but where did the oil go... Thought about the placement of the gasket on the filter cap... and that seemed fine.... no oil leak in our driveway.... even placed a piece of new cardboard under the motor after the oil change and ran it for about ten minutes and then got in and ran it for awhile at 2000 RPMs thinking maybe it would leak somewhere under pressure???? Nothing.... obviously will check the oil more often now but the motor runs fine.... what happened to the other two quarts? Rings??? and yet, no blue exhaust etc...

The car owes us nothing.... and with 200,000 miles, it might be time anyway... but it is our grocery getter... and would like to keep it around...

So the question.... am I missing something? or should I be looking for something else? and finally.. .yes, the underside of the car is still clean enough.... I have seen cars that leak oil and the underside is an oil slick.... that is NOT the case here either...

Any suggestions welcome.... thanks....

 

Well if there are no leaks and it's not in your coolant, then it must burning it. Just slowly enough that your don't notice.
You could try some oil system treatment to free up the oil control rings in case they're stuck.

 

This actually happened one other time a couple years ago and hasn't happened since. We didn't know why the oil was so low then or now... I do know that I am going to check the oil each time now before and after we take it out and monitor it. The car doesn't owe us anything but we would like it to keep going for a few more years. You know, Murphy;s Law... we just put a set of brand new tires on the car. I agree with you on the three possibilities....

 

Maybe check it weekly for the next couple months to get a better idea of what it's doing