The McLaren driver’s fastest time was over 1.5s faster than the next-best effort, set by Nico Hulkenberg of Force India.
“It’s a dream every time I get in the car: it’s just so cool to be here and to be driving - I’m really enjoying it," said Magnussen.
“Unfortunately, we didn’t get too many laps done this morning, but it was good to get some laps done at the end of the day. The afternoon was good for us, and we worked through our problems.
“The team is doing a great job to help me: they’re giving me really good guidance and making me feel confident. There’s a lot of discussion about laptimes, and it feels good to get some good times recorded, but winter testing is just that – testing. It isn’t about times.
“We’re still learning a lot about the car. We have four more days of testing next week and there’s still a lot of work to do. I’m sure everything up and down the pitlane will change a lot between now and Australia."
Hulkenberg, Wednesday's pacesetter, completed 13 more laps than Magnussen - 59 - but not as many as Ferrari’s Fernando Alonso who racked up 97 circuits for the third fastest time of the day. The Spaniard started the morning with some aerodynamic tests, before undertaking a detailed evaluation of adjustments made to all the operating systems linked to the power unit, including energy recovery and release
Mercedes’ Nico Rosberg posted the fourth best time on the board, despite causing two red flag periods in the morning when his F1 W05 stopped on track with technical problems.
“Our day today was slightly troubled compared to other recent days; however, we still managed to get a lot of mileage done,” said Mercedes’ technical chief Paddy Lowe.
“We experimented with the medium tyre and found this to be a slight improvement on the harder compound with more consistency. We're working to understand the issues that delayed running at various times throughout the day and this is exactly why we go testing as it gives us a good chance to resolve them before the racing begins.
“It's pleasing to see that all the Mercedes-Benz powered cars are achieving good mileage up and down the pit lane, which gives us a great base to work from going forwards.”
The busiest driver on circuit on Thursday was Williams’ Valterri Bottas who made it around the Sakhir track 116 times in the Mercedes-powered FW36. The Finn also recorded the fifth best lap of the day as the Grove-based team made up for the time they lost on Wednesday with technical gremlins.
“Having spent yesterday dealing with an apparent fuel system problem we tracked it down to a wiring-loom manufacturing issue late last night,” confirmed Williams’ chief test and support engineer, Rod Nelson.
“With this repaired the result was the mileage that we achieved today. We are still getting to know the car performance wise, but it's good to see that we are getting some good reliability out of it. Every time we run the FW36 we are understanding it more and more. We tested some aero components and systems this morning before completing a race simulation this afternoon which, aside from having to stop briefly for a red flag, went to plan.”
Behind Bottas, Kamui Kobayashi staged a late charge for Caterham to lift himself to sixth on the timesheets, one place above reigning world champion Sebastian Vettel.
“It’s still too early to know where we really are, but being able to build the mileage every day is the only way we’ll be able to get the most out of the car,” explained Kobayashi.
“Reliability is going to be so important this year, and it’s good that the issues we’ve had here have been fixed well enough to allow us to keep running. It’s also good to finish the day with a relatively quicker lap, but even though everyone knows lap times don’t really mean anything in the tests, it’s good for the team to start to see us unlocking some of the car’s performance.”
After more car troubles on Wendesday, Vettel was finally able to register a healthy lap count, with his Thursday tally of 59 more than Red Bull had achieved over the five previous test days combined.
“Definitely a better day today,” said the German, who will hand the RB10 over to team mate Daniel Ricciardo on Friday.
“We did more laps, so that’s encouraging. It’s good to check the car, check the reliability, but obviously there is a lot still to do. It was good to get a proper first feel for the car and it feels OK but there’s a lot more to come.
“It’s difficult to talk about catching up [to rivals] because I don’t know what other people are doing, but we did more laps than we have done so far and that’s the big thing. We’re learning every single lap, even if the quality of the lap is sometimes not the best. However, the most important thing is to run and we did that. The last two days have been very useful. I hope Daniel can get some more good laps in tomorrow.”
Red Bull’s sister squad, Toro Rosso, also enjoyed a better day of activity as Jean-Eric Vergne completed 58 laps in Renault-powered STR9 for eighth place overall. The Frenchman’s best time was marginally quicker than the fastest lap that Esteban Gutierrez could muster for Sauber, but the Mexican’s afternoon running was compromised by an electrical problem on the C33-Ferrari.
The final two slots on the timesheets were occupied by Lotus’s Romain Grosjean and Marussia’s Max Chilton, both of whom failed to break the 20 lap marker because of technical issues.
Unofficial Thursday test times from Bahrain
1. Kevin Magnussen, McLaren, 1m34.910s, 46 laps
2. Nico Hulkenberg, Force India, 1m36.445s, 59 laps
3. Fernando Alonso, Ferrari, 1m36.516s, 97 laps
4. Nico Rosberg, Mercedes, 1m36.965s, 85 laps
5. Valtteri Bottas, Williams, 1m37.328s, 116 laps
6. Kamui Kobayashi, Caterham, 1m39.855s, 66 laps
7. Sebastian Vettel, Red Bull, 1m40.340s, 59 laps
8. Jean-Eric Vergne, Toro Rosso, 1m40.609s, 58 laps
9. Esteban Gutierrez, Sauber, 1m40.717s, 55 laps
10. Romain Grosjean, Lotus, 1m41.670s, 18 laps
11. Max Chilton, Marussia, 1m42.511s, 17 laps