Lewis Hamilton made his testing début for Mercedes at Jerez on Monday.
Mercedes conducted promotional testing - every team is permitted up to 100km - with Nico Rosberg handing over to Hamilton.
"It was not too bad, it just felt like driving a different car," Hamilton told Sky Sports News.
"I am not sure what else to say, there is a lot going on, a lot of new controls I am getting used to and so much information coming in and just trying to get on top of it."
"The steering settings that I had before are very different on this car and there are a lot more buttons as well. So utilising those and understanding the set up changes that they make - the diff settings."
"All the calls are different - they use different terminology on top of that and the car brake bias has six settings instead of the three I used to have so there is a lot of different stuff going on."
"I've driven the simulator a few times, but this was the first time I got to get a feel for it and also the tyres weren't the right tyres."