In CA you will often see in the news and in idle conversation warnings about slick roads when it rains. If you’re not a native, this is somewhat bemusing. Duh?
But wait! The natives say - in CA oil and gas build up on the roads making them much more dangerous than you are probably used to!
I don’t think anybody disputes the idea that oil+water is slick, but having lived in CA for over a decade now I really haven’t seen any evidence that CA roads are significantly more slick than anywhere else during rains due to this supposedly dangerous “oil build effect”.
Is there any objective data on this?