0-20 w oil= sewing machine oil...just how tight can they make bearing clearances? I have been hearing this for the past 10 years..how tight can you go before you get metal to metal contact with rod and main bearings ?
I have an 89 Mustang GT 5.0 and have been running 20w-50 all year round in Florida and had car since brand new has 208k on it and never touched the engine, runs like it did brand new and never had to add oil between changes.
These new motor oils are garbage for older cars..I belong to a classic car club and have had many members getting wiped out camshafts using these modern oils. Ford 460's, FE blocks and chevy 327's etc. using newer 10w-30 oils
I am not saying that these new oils are no good for newer vehicles.
In my 59 T-bird and 74 Nova run straight 30w all year round.