Our travels throughout two states this week found engineers busy testing both the recently introduced Opel Insignia (photos 1 through 4) and its upcoming near-identical twin, the all-new Saturn Aura (images 5 and 6). Both models have very similar – yet unique grilles, and the Saturn is proudly wearing U.S. spec headlamps.

Although testing has obviously not slowed, production and on-sales dates for the Saturn are currently “in the air” – as sources from GM’s Fairfax, Kansas, plant have leaked.

Sources are guessing that fuel economy and CAFE Standards may be responsible for the indefinite delay.

The upcoming Aura/Insignia is based on GM’s fresh Epsilon 2 platform. We’re expecting similar powertrains to the current model - a couple of V6s and a hybrid - as well as front wheel drive. All wheel drive is a rumored possibility. However, the delayed launch of the Aura could mean GM is working on a new four-cylinder for the mid-sizer.

Previous spy shots show the prototype’s gauge cluster is highlighted by four chrome-ringed dials — two large and two small — with clean looking faces. Chrome also accents the center-mounted gear shifter, giving the interior an up-scale feel. Although the quality doesn’t look quite up to production floor standards, the overall design can be inferred. Atop the center stack looks like a space that could house an LCD screen.

The Aura was originally expected to launch in mid to late 2009, but that launch date has likely been pushed back to sometime in 2010.