No ones mentioned viscosity, what do you think the numbers refer to ?
Ford recommend a 30 weight oil for the cossie, maybe they have shares in oil companies as this is wholy unsuitable for the yb, some use thicker higher viscosity oils so they are not as thin when heated compared with lower viscosity oils, I prefer the approach of cooling the oil more, I saw temps of 130C at a steady 70mph on my 2wd, when using the std oil/water cooler, which bears out what new york uni found, on average oil is 30C hotter than the water, as it does at least as much cooling.
I still run engines in on mineral oil, even though I know a modern synthetic does NOT stop a engine wearing in properly, being too easy does though.
tabetha