After seven years at Yamaha, Valentino Rossi began a new era with Ducati at Valencia on Tuesday.
Delayed by morning rain, Rossi left the pits on a black Desmosedici bearing his famous #46 at 12:20 local time.
It marked the start of a new adventure in which the Italian will try to become the first rider in history to lift the premier-class crown for three different manufacturers.
Rossi rode for a total of 56 laps, with a best lap time of 1min 33.882sec.
That put him tenth out of the 17 riders and compares with his best Yamaha lap from Sunday's race, which he finished third, of 1min 32.970sec. The overall best lap time on Tuesday was 1min 32.012sec, by Rossi's former team-mate Jorge Lorenzo.
As rumoured, seven-time MotoGP champion Rossi tried both a 'big bang' and 'screamer' engine.
Rossi used a 'big bang' Desmosedici GP11 for virtually the entire day, as he worked on geometry and other settings, then made one final run on the 'screamer' version.
Rossi raced with a 'big bang' engine throughout his Yamaha career, and Ducati also used the technology in 2010, but are prepared to switch back to the even-firing screamer if the Italian prefers it.
The Doctor is unable to speak publically about the test due to conditions placed on his early contract release by Yamaha, but Ducati Corse general director Filippo Preziosi was able to comment on a day that will go down in the factory's history.
“It has been an exciting day for sure. The main thing that hit me today was Vale's positive feedback and his capacity for analysis," said Preziosi. "Today he tested the GP11 with the 'big bang' engine on a standard setting, which he modified step by step to adapt it to his riding style.
"His first comment when he lifted his visor up was a positive one about the power delivery and then he gave some impressive technical details. We certainly have a lot to do to adapt the bike to his riding style but it is really nice and very interesting to work in this way.
"We worked on the geometry and setting today to see how the bike responded and to get a bit of experience working with both Vale and Jeremy [Burgess].
"At the end of the session he went out on the screamer version but we will make more of an analysis between the two engines tomorrow because they deliver the power in very different ways - the big bang has a more regular power curve whereas the screamer is more aggressive but also more powerful.
"Nicky [Hayden] tried both versions today and this evening we will have a look at all the data.”
Hayden, who was ninth fastest, indicated that it won't be an easy choice.