Huh?? It's a RR engine. Nothing GM about it, unless you count the AC compressor on the top of it that says, "AC Delco".
They are expensive cars to own, even if you get one for free. Figure on 1 dollar per mile in maintanence costs. They were designed for rich people who do not even look at their repair bills, this does not change as they get older. Except that they get more expensive as you go. That's the reality, sorry if it rains on the parade. It's a gift that you would give someone that you really hate.
Did I mention ~8 mpg on premium?