He spent the morning practising pit stops and aerodynamic assessments before recording his best time of one minute 25.837 seconds after an engine change - 4.5 seconds behind pacesetter Michael Schumacher for Mercedes.
Ferrari's Fernando Alonso trailed the German by 0.346 seconds, while Red Bull's Sebastian Vettel finished 1.665 seconds off the pace.
Although Button said he was disappointed not to get more miles under his belt in testing, he is looking forward to the season's first race.
"We had an engine change over lunch which took a little bit more time than we thought so I haven't got a lot of running done really," he said.
"But I think after Tuesday we were quite positive with the direction we've taken with the car and I think there is more to come in Australia."
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