Adrian Newey admits it is harder to find gains for 2013 car

The maturity of the regulations, which were introduced in 2009, and the lack of rules tweaks for next season mean that teams are chasing ever-shrinking improvements with their cars.

The Red Bull has been the dominant force under this rules set, winning the drivers' and constructors' championship double three times in four years.

"It is increasingly difficult because there are no real regulations changes compared to this year and it will be the fifth season since the 2009 rule changes," Newey told AUTOSPORT.

"The field is converging and you can see how competitive it is in the fact that we had eight different winners this year."

Newey believes that the number of winners in 2012, which is the largest since 2003 when eight drivers also tasted victory, shows how tiny the margins are in F1 currently.

Six different teams won races, with Red Bull, McLaren, Ferrari, Lotus, Mercedes and Williams all tasting success.

"It is a demonstration of how critical it is now," said Newey.

"Each race, you have so many variables that can cause swings between the cars.

"The tyres have been talked about a lot and they are important ans each car will work its tyres slightly differently compared to its competitors.

"Sometimes, a particular track layout and temperature might suit a particular car more than its immediate rivals.

"Whether it's a predominantly high-speed corner circuit like Silverstone or a slow-speed corner circuit like Abu Dhabi, for instance.

"Those factors mean that it has been difficult for one team to dominate."

Newey added that next year's Red Bull RB9 would be an evolutionary step from this year's machine.

"There will be no surprises, next year's car will be very much an evolution of this year's," said Newey.

"The great thing about motorsport and F1 in particular is that we know what we are intending to achieve over the winter but we have no idea of what everyone else will manage."

Red Bull's dominance 2009-2012

Drivers' championships: 3 (75%)
Constructors' championships: 3 (75%)
Wins: 34 (45.3%)
Poles: 46 (61.3%)