F1: Hamilton admits there is room for improvement at Mercedes

Lewis Hamilton stops in pit lane during day three of Formula One Winter Testing at Circuit de Catalunya on Feb. 21, 2015 in Montmelo, Spain.

Mercedes continues to fly under the radar in preseason testing, and once again Lewis Hamilton stuck with medium tires while others used supersofts to set quicker headline times.

Hamilton says he’s still not feeling quite right after a fever forced him to miss Thursday’s running, although he did log laps on Friday.

"Just like yesterday, there have been better days in terms of how I’m feeling," said Hamilton.  "I’m definitely not 100 percent and I’m looking forward to going home tonight and sleeping for the next couple of days. It was a hard day out there physically – but I’ll make sure I’m better for next week and come back stronger. I’m glad I got some good time in the car today with 101 laps.

"We weren’t looking for a quick lap, just driving round looking at setup changes. If the weather had been better we would have had more mileage but we got through everything we wanted to today anyway. All things considered it’s been a great day."

Like other drivers Hamilton said he had trouble getting the tires up to temperature.

"The biggest issue at the moment is actually getting the tires working properly. There’s temperature in them but they just don’t seem to ever be in the operating window. Hopefully when we see warmer temperatures they’ll be better.

"The car itself feels solid and we’ve been good on reliability. There are areas we can improve on, but we’re taking it one step at a time and each step so far has been forwards, not backwards, so it’s been quite positive."