Jorge Lorenzo edged out team-mate Valentino Rossi by just 0.070sec for a Fiat Yamaha one-two during the first day of testing at Jerez in Spain.
The final MotoGP pre-season test got off to a wet start with rain descending on the Jerez circuit on Saturday morning, prompting Rossi to stay in the pits until just before 2pm, by which time conditions had improved.
The reigning six time world champion was thus the last of the 19 riders to take to the drying track, but he soon replaced Ducati's Casey Stoner at the top of the timesheets.
However, 2008 MotoGP rookie of the year Lorenzo - who qualified on pole for last season's Spanish Grand Prix - was able to nudge Rossi aside in the closing stages, handing the local star an important psychological boost heading into Sunday's qualifying shootout, when a new BMW will be up for grabs.
“I am very satisfied because I have improved through every hour of the day today,” said Lorenzo. “In the beginning it was quite difficult because there was rain this morning and the track was wet, but after lunch I was able to improve and was fastest for most of the afternoon and able to put in a great performance.
“I rode many laps - the same amount as my new number in fact  - and I was able to confirm the good feeling that I had on the last day in Qatar, when I was second. We still need to keep working, this is just the beginning, but I think we're going in the right way.
“Tomorrow I want to make one more step, but I am not thinking about winning the car,” he insisted. “With regards to the Bridgestone tyres, I think the front is very different and you are able to go faster into the corners. I hope the sun shines again tomorrow!”
“We had a good test here in November and also Malaysia and Qatar were good, so today it seemed that the trend is continuing,” added team manager Daniele Romagnoli. “We are now at a very important stage because this is the last test of the season, because of the new rules, so tomorrow is going to be crucial!
“Tomorrow will be an exciting day because it is almost like a qualifying session, with a prize, and we hope to finish in the same way as today! Of course at the same time we will continue to work on our bike to ensure that we're completely ready for the first race.”