BMW will not launch a hybrid vehicle unless "it is more economical in the real world than a diesel car," a senior company engineer has told Autocar.The comment reveals the frustration felt by many in the European auto industry that hybrid vehicles have become near-synonymous with environmental friendliness, despite often returning poorer economy than rival diesel-engined cars."Hybrid cars are very good for slow and stop-start driving but not so good at higher speeds. Overall, our diesel vehicles are still more economical," said the BMW source.BMW’s first hybrid vehicle is expected to be a version of the next-generation 5-series, closely followed by an updated X5, and this information would seem to suggest that it's likely to be diesel- rather than petrol-electric. Although BMW didn’t confirm the hybrid’s identity, it did say that the first model would be launched in 2010.BMW has joined forces with DaimlerChrysler and GM to engineer a rear-wheel drive hybrid powertrain that can be fitted to a wide range of future models. Recently, a respected German automotive magazine revealed that over a 60,000-mile long-term test its 1.9-litre turbodiesel Skoda Octavia averaged 41.5mpg, marginally ahead of the magazine’s Toyota Prius, with added benefit of better performance and greater load space.It’s understood that gap between the real-world economy of larger hybrids such as the Lexus GS and BMW’s 5-series diesels is even more marked.