DS is *definitely* not allowed to watch the news, nor does he watch live tv (pre-recorded stuff off the DVR, or things my husband has downloaded for him). I am pretty sure he learned about oil at school. This isn't the first time they've introduced topics at school that have sent DS's brain into overdrive (solar flares!? deforestation!? etc).
Sadly, the 'It's going to be fine, don't worry about it' answer rarely, if ever, seems to satisfy him.
We do try to do charity work and donations, to show him how you can actually help, but some things, like oil, just seem to be too abstract to do much about. (Abstract's not really the right word there, but it's Friday...)