London, May 6 (IANS) Some diesel cars are beating the over-hyped hybrids in terms of fuel efficiency.

 
 Toyota's petrol-electric Prius, which led the race for hybrids a decade ago, achieved fewer miles to the gallon than a sporty BMW 3-series diesel, according to consumer watchdogs.
 
 Many more diesel cars are running neck and neck and giving the hybrids a run for their money, the Which? Car magazine research shows.
 
 And with customers generally paying a premium to buy a hybrid, which is generally a few thousand pounds more expensive than a standard petrol or diesel model, the extra cost of the car may outweigh the fuel saving, the Daily Mail reports.
 
 The Prius is called a 'hybrid' because it combines a 1.8 litre petrol engine with an electric motor, which work seamlessly together.
 
 The electric motor operates as a generator to help recover surplus energy, including from decelerating and braking, that would otherwise be wasted. This energy restores the charge of the high-power battery, which in turn can be used to power the car's wheels.
 
 The latest edition of Which? Car looked at the actual fuel efficiency achieved in 'real world' driving rather than the claims made by the manufacturers.
 
 This showed that in its tests a BMW 320Ed small executive saloon managed 64.2 miles to the gallon (mpg)  ahead of the Prius's 61.4mpg. Over a year's driving of 12,000 miles, the BMW will cost 1,120 pounds - or 51 pounds less than the Prius at 1,171 pounds.
 
 The Prius and other hybrids rely on one major leap forward in technology.
 
 The BMW relies for its fuel efficiency on what it terms 'efficient dynamics' - that is making lots of small efficiency gains across the length and breadth of the vehicle - from lighter seats or chassis to more frugal engines - which, when put together add up to one major gain.