no, you tear down both engines and measure it against new spec, the one closer to new spec is the winner.
and what sort of idiotic, moronic and jaahil thinking says that opening an engine will cause damage - do you not repair the engine when its leaking? Or just let it roll with leaks because "jenyan sealed panni pack hinjan hai"
Its an engine made by an auto manufacturer by the million count, They have even published its service and repair book which is written so even the simplest of simpletons can repair said engine to "factory specification" with the tools mentioned in the book.
IMC filled the old diesel corolla with straight SAE40 and SAE50 oil from the factory and were even selling SAE40 oil at the dealership, There was a massive no. of complaints from KPK and Azad Kashmir areas that the damn car wouldnt start in winter - no shit it wouldnt start, the oil was like glue. - Im sure you never heard of these complaints either.
Toyota spec SAE40 to be used in the 2C diesel when the engine is used in a standalone environment only - that too with preheating of the oil - not in passenger vehicle use. But IMC did this SAE40 gimmick just to satisfy local users - of "mota haail"
when choosing an oil - the first number is used to select cold start ease, and the second number is warmed up engine oil viscosity and its best to use the manufacturer (not assembler) specification. Toyota tested that the w30 SAE spec viscosity range is "proven to them" for ideal service and fuel economy. The 0W20 versions of the same engines have a slightly larger sump (abt 1 litre more) - and may or may not have cooling jets for pistons. The larger sump is more for longer drain interval and a bit extra cooling. (toyota spec a 10000 miles drain interval now)
I own a really ancient camry - its a 2002 (same one I repaired the block myself) - it has a 2.4 litre engine and is specced for API SL 5W30 - I put the cheapest discount 5w30 I can find in it (or free oil sometimes) with filters bought in cartons (supremely cheap), oil is changed at 4000 miles (6400 kms) - it holds 3.8 litres only.
it still has 18 psi oil pressure at full hot idle, engine compression at 195 psi on all cylinders - mileage is at 184000 miles (294000 kms) - I repaired the engine myself at 125000 miles while not paying attention except for torque values and valve shim clearances.
I live in Houston TX, where its hotter than satan's armpit in the summer. and I use regular 87 octane fuel in it, Is my car magical or am I using some magic oil?