BMW has always backed economic diesels in favor of petrol-electric hybrids when it comes to building fuel efficient drivetrains, however, a senior engineer has confirmed the carmaker will launch a hybrid vehicle but only if it proves more economical in real world conditions than its diesel counterpart.

The latest diesel powered cars have already beaten hybrid vehicles such as the Toyota Prius in the mileage stakes, and the oil-burners easily trump cars such as Lexus’s GS and LS hybrid sedans in the large car segment as well. Speaking with UK publication Autocar, the BMW source admitted that hybrid cars were better in slow moving stop-start traffic, but in real world driving diesels are still more economical.

BMW and its main rival DaimlerChrysler have joined forces to develop hybrid drivetrains, with the latter making the bold claim that a hybrid option will eventually be available across its product range. BMW’s first hybrid vehicle will most likely be the next-generation 5-series sedan, which may be followed by a hybrid X5 in 2010, and both cars are expected to run a mild-hybrid system utilizing a diesel engine rather than a petrol unit.