What causes an engine to eat oil?
 

My engine is getting up there in age (160K on the odometer) and it tends to eat about a half to 3/4 of a quart of oil every 3 months. I have to dump some in the keep it topped off. The car doesnt blow any smoke what so ever, and it performs well with no sluggish behavior and no leaks anywhere. Could it be bad rings? I've done compression checks and everything is good on that end too.

plenty of things can cause oil to burn

rings
valve stem seals
etc

its age man realize that 1/2 quart over the span of months really isnt that much plus the fact that its goin into the cat anyways and its getting heated and burned there

^^That

I wouldn't worry too much. And you wouldn't notice burning that little oil at a time.

It is probably due to your engine showing it's age, but I don't think it indicates that you'll have a problem anytime soon.

If it really concerns you and you're not currently you can switch to a high mileage oil. They tend to get consumed at a lower rate than thinner regular oils or synthetics.