Wife and I have-had 13 new vehicles since 1970 and always used the 3k OCI religion when new.
Never a problem and all badly rusted vehicles were driven to junkyards around 20 years later..... still running well and not losing more than a quart in a 3k OCI. They probably averaged 300k in mileage.
Will we see 300k on these-2 Hyunkias we own now?...... no way Jose! Not even 175k on our-2 city-driven vehicles. These-2 historically shed debris from birth until death.... lol. I bought both of these to test and show the world I will beat the odds of the 2.0 and 2.4 being labeled junk engines. Boy was I nuts thinking that.
I am going to lose this bet, unless the wife finally agrees to sell these-2 Hyunkias premature of old age. Otherwise, they may be only 10-15 years old with 175k, when towed to a junkyard somewhere because of a grenaded engine. Or, in 10 more years, my Atrial-Afib and her Aneurysm will have finally put us in plastic bags.
How long will engines live on 0w8 oil?....... depends on the individual engine manufacturer's history. The Sun may darken every day at Noon, before we see Hyunkia Owners Manuals stipulate 0w8 oils.