Greed may be a reason, but I doubt it. The main reason for increased oil prices is GOVERNMENT sticking it’s nose in an area which should be off limits to government. In fact, most prices are higher because of GOVERNMENT GREED, not business greed.
Of course the price per gallon would be lower without government taxes, but I am not so sure that they are the epicenter of price increases sans taxes. The government actually receives more than the oil companies per gallon IIRC. Prices go up mainly due to speculation and if you’re selling crude oil, the more speculation the better.China increasing demand greatly is a big factor as well.
I didn’t specify the origins of the greed.