Compression test all cylinders to see they are within 10% pressure of each other. If any one or two have a big drop you could look there.
My first thought is if you have oil in the water, wonder if you have some anti-freeze in the oil too from the same issue?
Anti-freeze settles to the bottom of the oil pan, so it is the first thing out when you pull the drain plug quick for a look see.
Also there is a gasket at the aluminum timing cover where oil could meet water if it is leaking, not sure on this as the cooling system is pressurized, that would push water to oil not oil to water jacket . . but can check.
View attachment 1715553828
Process of Elimination, just have to keep ruling things out as you are diagnosing the different areas and systems of your car. Trying to figure out where and how oil could pass into the water jacket.
Also automatic trans cooler in bottom of radiator can leak oil into cooling system easily if faulty.
