The catchword "hybrid" is being spoken and written about everywhere. Originally introduced by Toyota, the technology was hailed as a silver bullet in the fight to cut fuel consumption.German carmakers including Mercedes and BMW have since introduced their own hybrid models. But does the technology really deliver what it promises? Or is the good old diesel engine perhaps the more frugal option? drive it! designs a test pitting the 7-Series BMW diesel against the hybrid version of the same model.