Red Bull's Daniel Ricciardo finished the day third on the timesheet, but development is more important than outright speed at the end of a testing day.
The Aussie was satisfied with conclusion of his programme - especially on the aero dynamic front - despite suffering an engine failure which took deprived his schedule of mileage.
"It was a good outing for the aero department – we did a lot of data gathering in the first hour, which all went to plan, and that’s important for the guys, even though for a driver it’s not the most thrilling thing, as you’re just trundling around really!
"After that we did a few runs on the soft tyre and made a few mechanical changes, which were interesting, we then completed a couple of runs on the supersoft.
"I think we discovered a few things there. You do try some bigger set-up steps than you might do on a race weekend and it was interesting to see what the results of those changes were.
"We were planning a few long runs in the afternoon but obviously the power unit issue prevented that."
Tomorrow, Max Verstappen will take over the RB13 which will be fitted with a new Renault power unit for Wednesday's session.
GALLERY: All the action from the Day 1 in-season testing at Bahrain
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