If there's a societal collapse, or a crash in oil production, (or both) petroleum based fuels are going to be very difficult (and dangerous) to come by. You can only store up so much gasoline and/or petroleum based diesel fuel. When your generators and vehicles run dry, that's it.. You're done. The best way to prepare for this is to utilize equipment that runs on diesel and learn to make your own fuel from new, or used vegetable oil. It's cheap, easy to make, and as long as you have access to a few easily obtained ingredients, you can make all you want.