Volkswagen XL1 prototype - front three-quarter view

Earlier this year, we caught the Volkswagen XL1 testing in some cold-weather climates, and as the ultra-fuel-efficient hybrid gets closer to production, some more spy photos have surfaced showing the car performing hot-weather tests. A production version of this diesel plug-in hybrid car is expected to return 235 miles per gallon, and it could be on sale in limited numbers by next year.

Looking very much like the 2011 Volkswagen XL1 Concept, this prototype stands out with its streamlined shape and its inset, narrow rear track. The last time we saw the XL1 in prototype form, it had door mirrors mounted outside the car either as camouflage or in place of the side cameras, but these latest shots show that the car will in fact rely on cameras for driver visibility. The lack of door mirrors should help keep the car sleek – Volkswagen listed the concept's drag coefficient at just 0.186. This car is also missing the full rear-wheel covers that will give the car optimal aerodynamics.

With the gullwing-like doors open, we can also see some of the interior, which has a very similar appearance as the concept including the large gauge cluster, navigation screen, shift lever and center stack controls. The instrument panel and A-pillar look to made from carbon fiber. One thing we can't see from this shot is the arrangement of the passenger seats. The concept car featured an offset seating configuration, and it isn't clear if this will carry over to the production design.

From these shots we can also see into the rear engine compartment showing a large cooling fan over what is expected to be a small, two-cylinder diesel engine. This efficient engine combined with a 27-horsepower electric motor and seven-speed DSG transmission is what will help give this car its triple-digit fuel economy numbers.