How old is Oil?

Oil, coal, and natural gas are "fossil fuels." I remember being a kid, thinking it was nifty we could be burning a brontosaurus in my dad's pick up truck. Sinclair Oil had a dinosaur logo. But I wonder--has anyone ever bothered to carbon date oil? I know there's carbon in it, is there any reason it can't be tested?

I'd think an oil company would want to know how old oil really is, because knowing that will help their geologists find new oil--if it comes from the cetacious period, that tells you something about how deep to drill. I've heard that the Russians believe oil isn't a fossil, but an extrusion of carbon from Earth's mantle--that oil is just carbon gunk that happened to be in deep as Earth was forming. If that's the case, oil would be more likely to seep upwards (towards where we can get to it) along a spreading intersection of tectonic plates.