The final day of testing at the Valencia circuit would see Nico Rosberg finish third fastest driving the new FW28. Nico's day was spent focusing on tyre testing for tyre supplier Bridgestone. Unlike previous days Nico was able to complete his programme without any mechanical failures. The only minor glitch was when his car ran out of fuel.

Joining Nico was Brazilian driver Joao Paolo de Oliveira, who was making his Formula One debut with the WilliamsF1 team. He would use the teams interim FW27C. He would complete thirty two laps and would finish at the bottom of the times. Oliveira said after the test: "I am just stunned and I am so happy and I really thank the team for this chance,"

WilliamsF1 Technical Director Sam Michael:
“Today was the end of the first test for the FW28. It was a really good start for the new car, with no major problems that you might expect on a first run. We also completed a few aerodynamic tests and confirmed that everything on the new car is working as predicted by the wind tunnel. Nico finished mid afternoon today, as planned, after starting some aero and mechanical set-up work. We also found a couple of good directions from which we can get the best out of the Bridgestone tyres which we will now work on in time for the next test at Valencia.

João Paulo de Oliveira drove the FW27C for us today to put mileage on some of the engine and gearbox components. It was his first time in a Formula One car and he did everything well. The team now head to Jerez for a four day test next week with two FW28s, Webber, Rosberg and Wurz will all be on duty.”

Simon Corbyn, Head of F1 Race Engineering, Cosworth:
“The Cosworth CA2006 V8 experienced no engine installation or cooling issues when installed in the new Williams FW28. This is quite an achievement given the incredibly tight packaging and demonstrates how effectively the Williams & Cosworth engineers have been working together during the design process. We have not yet validated all the Bahrain GP specification components at the track, so we will therefore have some further engine reliability and performance updates to evaluate in Jerez next week.”

Alex Wurz:
“I had two very interesting days this week during which I was able to confirm some of the directions we want in terms of tyre development. Importantly, we worked on the electronic set-up of the traction control system and engine response. Now I can't wait to drive the new car and start working on that.”

João Paulo de Oliveira:
“Overall, I was very satisfied with today’s test. What I found most impressive was the car’s brakes, but they were also the hardest thing to learn as I’ve never done left foot braking before. The team made a few adjustments in time for my last run, which made it a bit easier. It was such a great experience and one I’d love to do again sometime.”