Romain Grosjean wants to conclude the 2015 season with the "greatest high possible" as he prepares for the final five races of his tenure at Lotus before moving to Haas F1.

Grosjean was confirmed as Haas' first driver this week ahead of the American team's debut in 2016. He moves despite Renault's impending takeover of Lotus, with the Frenchman admitting he was not willing to wait for the protracted talks to be completed.

Grosejan returned Lotus to the podium at the Belgian Grand Prix for the first time since 2013 and he wants to finish the current season in the strongest possible fashion.

"Leaving Enstone at the end of the season won't be easy," Grosjean said. "I promised everyone some beers in December when I come to say goodbye to the factory. Until then we've got five races left yet this season and I'm absolutely determined to end my time with the greatest high possible.

"I'm headed to a new team and a new and very different challenge in 2016 - it's true - but it's going to be very emotional for me to leave the team that I've been part of for so long. I've worked with Enstone for 10 years, we had ten podiums together and I took part in nearly 80 races... I have to say that the people at Enstone are the strongest group of people ever to keep pushing no matter what the circumstances. I had to think long and hard for the next step of my career."

Grosjean is not ruling out a future return to Enstone.

"Part of my heart will absolutely always be with Enstone where I've grown and experienced so much over the years," Grosjean said. "I can remember turning up in September 2005 at the front gate, not speaking English and being very shy. Some of the people I met that day are still there. I'm turning a new leaf in my book but it doesn't mean that it's the end of the book so why not come back to Enstone one day to become world champion with the team!