What happens after the oil is gone?

Fossil fuel will not be needed in the new Messianic Millenium, soon to emerge after soon coming Armageddon, with King Jesus in the global drivers seat. The cities will have been reduced to rubble in the final mother of all earthquakes (global, see Revelation, last couple of verses in chapter 16). It's back to the horse and buggy with each growing each's own gardens and building each's own house to suit. Relatively "Few men" will be left on earth, as the prophet Isaiah puts it after the Day Of Jehovah's Wrath is fullfilled (Seven bowls of God's wrath poured out upon earth, Revelation 16). Satan will be in "bottomless pit" for the millenium and all's well without fossil fuels and need of industrialization.

Holmes, no sweat. Super climate similar to preflood will make the planet super productive with little need for motorized equipment, especially with every family growing own food.