[j_mo]

Yeah for this exact reason I despise torx. The last couple of cars I've owned have tonnes of torx screws, and as they rust and accumulate road grime over the years they change size. You will only be able to fit a T20 into an arch liner screw to start with, then as you turn it the rust and dirt dislodges, and it either becomes the next size up or cams out and rounds off. In weaker metals they round hilariously easily (torque wrench set to 20NM on a sump plug, torque wrench set to 7NM on a brake disc set screw).

My experience of Torx screws in high torque applications (bolting together Bosch high pressure diesel pumps) also makes them seem flawed, as the small contact area results in damage to the screw (hardened, awful to drill out, yet still round off with an almighty crack when enough pressure is applied, hence needing to drill out) or damage to the thin ends of the Torx driver itself 50% of the time.