Feb.20 (GMM/Inautonews.com) How much progress has dominant 2014 title winner Mercedes made over the winter?

The perfect man to ask on Thursday was Pascal Wehrlein.

A DTM driver, the 20-year-old German began his duties at the Barcelona test at the wheel of the Force India.

It is powered by Mercedes’ 2014 power unit, which was steered by works drivers Lewis Hamilton and Nico Rosberg to every race victory last year except three.

“As soon as I got used to the Force India,” Wehrlein smiled, “I was asked to drive the Mercedes.”

That was because world champion Hamilton did 10 laps in the new, 2015 works Mercedes before pulling into the pits with a fever.

The W06 is powered by Mercedes’ revised 2015 engine. How much better it is than the hugely-dominant 2014 version is one of the great unanswered questions ahead of the new world championship.

“Of course,” Wehrlein is quoted by Speed Week, “the two engines did not feel the same. But it’s hard to compare them.

“Over the winter everyone tries to get more power out of what they have, and of course that is noticeable to the driver,” he added.