never challenge the wisdom of 'FATHER' his choice was right at that time,
now stick to it. this forum is full of golfers playing over other men's golf bag without pay the caddy but just punching the keyboard. Some of them does not even have GUTs to challenge their regular ustad at workshop and kick under his belt to do what they learn from here.
if it has run 160000+ over 20W-50 rest assured with timely maintenance schedule over the same oil it will cross 200,000 without an issue.
Cheers & Salute your honorable Father doing the right thing at the right time.
if you rummage through Honda thread you will find few members accepting mistakes but failed to do as suggested because 'Ustaad Said that ' - as in replacing Radiator cap for Honda 1.1 to 0.9 which is not Honda spec but because Ustad wanted it.