Gas Prices

Oh boy, here we go again. The gas prices are going up. Thankfully, I just bought a new car that doesn't guzzle too much gas. I filled up the day before the hike started too. I assume though I will have to fill up soon. I just don't seem to understand it though, what is the reason for these prices going up? It seems just to be greed by the Oil companies. Might as well just invest in oil, it seems to be the only way to pay for gas these days.