Disclosed is an olefin containing stream from an oxygenate to olefin process, and a process for making olefin dimer and oligomer product from the olefin containing stream using a nickel based oligomerization catalyst. The dimer/oligomer product is optionally converted to hydroformylated product. The olefin containing stream that is used to make the higher olefin product has low levels of impurities including nitrogen, sulfur and/or chlorine.