New Lotus F1 chief technical officer Mike Gascoyne has admitted that the competitiveness and durability of the Cosworth powerplants the team will run during its maiden campaign in the top flight in 2010 is 'a big unknown and obviously a concern'.

As part of the deal for being granted one of the additional slots on next year's starting grid, the four newcomers - Lotus, USF1, Campos and Manor - all had to agree to using Cosworth engines, the very stumbling block that it is understood ruled Prodrive out of the reckoning, despite the David Richards-led operation being on paper comfortably the most well-qualified to take up one of the places.

Cosworth has a long and illustrious heritage in F1 stretching all the way from 1963 to almost the present day. However, the second-most successful engine manufacturer in the history of the sport in terms of race victories - behind only Ferrari - has not triumphed since Giancarlo Fisichella's belatedly-bestowed success for Jordan in the 2003 Brazilian Grand Prix at Interlagos. Indeed, the last teams to whom it supplied engines - Williams and Scuderia Toro Rosso in 2006 - between them notched up only twelve points season-long.

In theory, the reduced costs, ban on continuous development and more level playing field that are being gradually worked towards in the uppermost echelon should help the British tuner's return - but doubts remain about the likely performance of the 2010 package, and also its reliability.

"We're happy with what Cosworth has been doing," Gascoyne assured, speaking to Radio. "There are some unknowns - I think the biggest concern will be the four-race reliability with the engine, but until we've confirmed that we just don't know. The other teams have all gone from one-race engines to two-race engines to four-race engines and obviously have built up a huge knowledge database from that, whereas we're going straight in with an engine that hasn't run for two or three seasons and that has to last four races.

"That's a big unknown and obviously a concern, but we're very happy with the work Cosworth are doing and the way they're operating. Unfortunately, until we start racing we won't know how reliable it's going to be or what the ultimate level of performance is. We're working very closely with them, though, so I'm very confident that ultimately it will be a good package."