Originally Posted by
Colyx
You do realize that coal is still used as a resource for power generation these days? Check the english wiki for Coal#Uses_today as well as Electricity_generation - it's not just an ancient way to power things, it's still a major resource for power. In the US (as for 2014) electricity generated by coal is about 38%, natural gas about 27%, nuclear about 20%. In Germany it's 43% coal, 26% renewable (solar, wind, water, etc), 16% nuclear and 10% natural gas. Other countries have similar values, depending on their access to certain resources.
Petroleum (crude oil) is mainly used for transportation fuel (81%), for chemical industry (12%, plastics, lubricants, pharmaceuticals, etc), for heavy fuel oil (4%) and for asphalt (3%). Transportation fuels are gasoline (46%), diesel (26%) and kerosene (9%). Heavy fuel oils - those are the ones that are used for power generation. So you want to add petroleum/oil to the game, because of those 4%? In most countries this is about 1-2% of overall energy production.
So if petroleum/oil was added to the game, in order to be a legit resource, you would have to add a lot more: cars, airplanes, modern ships, chemical industries that use petroleum to produce different products etc. And while you add all these, coal consumption will have to rise even more, because all of them need coal.