How important is the oil market?

BP offers its own outlook of the oil market. In the report, it points out a potential increase of demand which could drive the oil price up. My question is how important the oil market is to our global economy. Of course, it is important to those oil companies and oil exporting countries, as low oil prices will damage their incomes. However, to what extent does the oil market directly affect the other economies? If the world economy is in good shape, the low oil price will be good to lower production costs. Moreover, when economic growth is high, oil prices are usually pushed up as demand increases. If the world economy is in bad shape, I think that low oil prices may only worsen the problem but are not the cause of the problem. I doubt about the effect of oil prices on the financial markets, I think it just reflects people's worries about the future economic performance but is not the cause of the core problem.