Damn, this is a tricky answer on this. As I'm sure you know 20/50 engine oil is designed for race engines! High sustained rpm engines that must hold up to higher heat from the stress of facing engines. When building a true race designed motor a ton of effort is designed into an expectation this engine must service 500 miles plus possibly another 100 on the outside. Never 100,000 miles of daily driving. No for emissions reasons all new engine design's keep tight clearances with expectations of little to no blow by etc . These tight clearances called for less viscosity as the spaces this oil was to pass through are not designed to give any space. Trying to push a 50 w oil through the limited space can best be compared to trying to suck a thick shake through a straw VS a soda through that straw! I fear you will find switching over from this oil at this point will likely result in clatter, potential oil burning out the tail pipe and heating issues. I have run in my 3 , 2.0 nothing but fully synthetic and the 5 w 20 it called for but have 75,000 miles less than you and live in warmer climate. I hope this helps. PS 45 years a mechanic wit ASE certs. So You could say I may have a clue on things.