Perhaps 20-50w motor oil might help a bit if the rings are tired. I've used that in some of my older motors and it seemed to help.
Long ago I had a 49 Plymouth with no rings left at all. To slow down the oil consumption I mixed my own blend of motor oil using 1 qt of 90wt transmission fluid, 1 qt of off brand STP, and 3 qts of 40wt reclaimed oil (it was really cheap and came in a five gallon tin). It lasted much longer than straight 30wt, but I had to push in the clutch when descending hills or it would lay down a smoke screen like a destroyer! Oh, and when it got cold I couldn't turn the engine over without leaving the car out in the sun to warm up first.
Not exactly an environmentally friendly solution today, but I was young, broke and going to school at the time.