Leclerc's best time of one minute 31.992 seconds was 0.879 quicker than McLaren's reigning champion Lando Norris, second on the time sheets, and fastest of the three-day second test.
"We ran through our program and tested all the things we planned to," Leclerc said.
"In terms of performance, it's still difficult to understand where we really stand because teams are hiding their true form, so it's important not to focus too much on lap times and prepare for the first race."
Mercedes have suggested Red Bull are the benchmark, and pointed also to Ferrari's rapid starts, while Red Bull have positioned themselves further down the pecking order and identified Mercedes as being a step ahead.
The reality should become clearer when the racing starts in Australia on March 8.
Four-times world champion Max Verstappen was third for Red Bull, 1.117 off the pace, pre-season favourite George Russell was fourth for Mercedes and Australia's Oscar Piastri came in 11th for McLaren.
Paistri said there is still a lot to get done between now and the season opener in his hometown Melbourne.
"I think we're probably getting a little bit more optimistic," he told Sky Sports.
"The testing has gone smoothly for us, we've been able to get a lot of laps in, learn a lot of things, both good and bad.
"I think round one (in Australia) is always important. So I feel like we're making good progress. Wouldn't say we're leading the pack by any stretch of the imagination, but feel like we're not too bad."
Alpine, last overall in 2025, had Pierre Gasly fifth fastest with Oliver Bearman sixth for Haas and Gabriel Bortoleto seventh for the Audi works team that has replaced Sauber on the starting grid.
Lindblad, the sole rookie this season, was ninth and set a record for laps in a single day in Bahrain with the Racing Bulls car looking solid with the new Red Bull engine. The most previously was 161 by Piastri last week.
At the other end of the table, troubled Aston Martin completed only six laps with Lance Stroll scheduled to be in the car all day but failing to set a time with the team sidelined by a battery problem.
"It's clear the car isn't where we want it to be performance-wise, and we know there's a lot of work ahead in the coming weeks and months," Stroll said.
with AAP
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