92 maxima using oil

Need help on finding problem. I have a 1992 Maxima se, bought new, changed oil every 5k miles. Did not use oil between changes. When I changed oil at 155k it was a Qt. low. Thought I had just put in 3 Qts at last oil change. Changed oil at 160k and it was 2 Qt low. Knew for sure I had a problem. Car runs fine, does not smoke and seems to have as much power as it ever did. New Nissan dealer said rings were bad. Anyone with any ideas ? Thanks for your help in advance. Sorry this post is so long.

Bob