454cid
Sooper Pooper
You'd know if the coolant was getting into the oil, it'd be milky grey.
Not always. If the engine is run enough, most fo the water will burn off, leaving only concentrated coolant in the oil. I had this happen on a work van that was run hard. The oil got sludgy and eventually started turning red from the dye in the dexcool. I'll admit, it probably doesn't happen often like that.
Why is it still pressurized after hours?
I wondered the same.
Mr Spock once said; if you eliminate all possibilities what remains, no matter how improbable, must be the solution (or something like that). What's left? You're burning antifreeze.
I think you've got the quote right.
One more possibility... could be in the transmission, assuming an auto. I'm still betting on a leak that isn't apparent. anti-freeze evaporate fast on hot cast iron.