Which does the TSX have? K24Z3 or J35Z6? The Civic Si has a K series right?In my commuters a 2010 Civic Si and my wife's 2014 Acura TSX I run nothing but Supertec high mileage. My Civic Si has almost 250K on it (I have a pretty long commute) my wife's TSX I think only has about 120K on it. They both run great with no issues I run the high mileage because honda engines are prone to leaking oil. Neither leak oil (had to RTV the timing chain cover, and put a new Vtec solenoid gasket on the Civic) or burn any noticeable amount of oil.
Pretty impressive reports on Supertech/Warren oils.