The engine supply market in the Formel 3 Cup is just as open. The H.W.A.-Mercedes and Spiess-Opel are the most popular, but some teams use the Mugen-Honda, TOM's-Toyota and even the older Sodemo-Renault. This is in stark contrast to the Euroseries, in which Mercedes powered all bar five of the 2006 entrants. However, the 2007 Formel 3 Cup season is likely to see a different pattern emerge, with the introduction of a new "Challenge" engine, which is expected to be chosen by a number of teams in both the Championship class and the Trophy class. It is being built by Spiess and is based on the company's Opel engine, but with some technical changes to lengthen the service interval and reduce running costs.