I'm not saying that a straight true bore is unimportant. I'm also not saying that ring tension is unimportant. What I'm saying is that an oversized ring fitted properly (end gap wise) to a mildly smaller bore will actually increase ring tension. It was designed to fit into a larger hole! when you put the same size circle in a smaller hole you have to compress it more, thereby increasing the tension. I was thinking he may have neglected to properly size the end gap, causing the ring to stick because of binding rings. I have used .010" over rings in standard bores probably 4-5 times, once on my own motor and run them hard for thousands of miles without problems. Granted this was in Harley motors, but the rings don't care what motor they're in! I can however se where a .040 or so difference could cause loss of circularity ( is that my own personal word?)affecting ability to seal, just not .010 spread over an approximately 4" bore! I have to believe that other factors led to this oil consumption, not the "loss of roundness" All rings are made into bigger circles than they are made to fit into. All piston manufacturers recommend a method of adjusting endgaps on their rings! Pistons, bores and all other engine parts can vary wildly from their manufacturing specs, therefore a wise mech. always checks them!
