The RB25DET is 12 years old, not rebuilt and ~150,000km old. The SR20DET is 13 years old, not rebuilt and ~90,000km old. Neither blow smoke. Both have excellent compression and make the power I'd be expecting from them.
I just find the thinner oils break down far quicker and end up thin and watery by the next oil change. The slightly thicker oil gives me a quieter engine and I drain almost exactly what I put into them out at the next oil change. A good number of 10W40 oils contain a lot of friction modifiers to achieve the desired viscosity, they're not fantastic for the engine.