Coal is definitely a fossil fuel. Quite a bit of oil is also. Methane doesn’t have any easy signatures to determine source.
Sorry... Oil is not a fossil fuel... unless you actually believe dead dinosaurs made all the oil.. same with coal...
When I first heard the term “fossil fuel”, I was in the fifth grade, and as a fifth grader I knew a line of crap when I heard it...
Oh, I also created a spreadsheet, and have proven mathematically, there were not enough dinosaurs over a couple of million years, to produce the known oil reserves of the world...
The theory, and yes, it’s just a theory, is false