I did a bit of research and it seems grease is grease is grease, more or less. .
A quick look on Wikepedia and here's a quick summary of why you're a bit off the mark-
Add into the equation additives applied to different grades of grease, with differing properties and specialised applications in mind. I'd stay well clear of your 'castrol grease' on any bearing, pivot or load bearing surface- suppose it could be warmed up and applied to a rag and then dragged through your frame tubes as a cheap way of protecting them against rust (only worth it on a steel bike mind!)...
It's dinged, scratched, used, abused, green and Canadian and the only ride I got- so I suppose I got to love it...