MotoGP rookie of the year Jorge Lorenzo was classified third fastest behind only Repsol Honda's Dani Pedrosa and his Fiat Yamaha team-mate Valentino Rossi, during the opening day of the Jerez test.
Both Pedrosa and Rossi set their best lap times with prototype 2009 machines, but Lorenzo - starting only his second test with Bridgestone tyres - chose to stick with a 2008 machine.
Lorenzo lapped one second slower than Rossi and 1.6sec slower than Pedrosa after 51 laps of the resurfaced Spanish Grand Prix circuit.
"Overall today has been a good day, even if the cold weather hasn't allowed us too much time on track," began Jorge. "It's only my second day testing since the new tyre rule and I think we're doing a good job so far, but we still have to improve because we're not yet sure of the perfect configuration for our bike with the tyres."
The Spaniard, winner at Estoril, also has a modified 2008 M1 available, featuring some new prototype parts, which he might try on Thursday.
"We are still using the 2008 bike with the old setting at the moment, I have a test bike with some new parts but we didn't use it today - maybe tomorrow," he said. "Anyway I feel good because I can see that we have the potential to improve more. The new track surface is a lot better, there are fewer bumps and so you can go faster and ride more how you want to. This is a good improvement to the track.
"Tomorrow it seems there is a chance of rain but I really hope not because we have a lot to do and I would like to leave here having improved further. This is a very important test because it's the last one until February, when we will have a new bike, so we need to gather as much information as possible for the engineers."