Crude oil prices have hit a four-year low after Saudi Arabia unexpectedly cut the price of oil sold to the US. Brent crude fell to near 82 dollar a barrel as worries about global growth also spooked investors. Earlier, the European Commission reduced its growth forecasts for the eurozone. Investors are concerned about the US oil industry in the face of slowing growth and lower prices. Some worry that low oil prices could hurt domestic US producers dependent on high prices for profitability. The price cut also sent shares in many energy firms lower, pushing down all three US share indexes.