Audi face a tough battle attempting to make history by winning the Le Mans 24 Hours with a diesel car for the first time, their driver Allan McNish says.
Audi are attempting to make history with their diesel car
The German marque are favourites having won the Sebring 12 Hours with their new R10TDI earlier this year.
But Scotland's McNish expects a tough battle with the French Pescarolo team.
"For us to compete with Pescarolo we've got to be seven seconds quicker than the R8 (Audi's previous car) was last year and that's a tall order," he said.
Audi's position as favourites owes a lot to their track record - they have won the classic sportscar race six times in the last seven years.
But is also down to the lack of a top-quality rival.
Audi's team are funded by the German car manufacturer, while Pescarolo are a private French team, albeit one with a strong driver line-up and racing heritage.
What we lose in some areas compared with the diesel, we gain in others
But McNish, who will partner seven-time winner Tom Kristensen and Italian Rinaldo Capello in a stellar line-up, does not underestimate the challenge his team face.
"We know what we can do, but we don't know what Pescarolo, Zytek and Creation are capable of," he said in an interview with Autosport magazine.
"I believe the Pescarolo is two seconds quicker than it was last year, and that was five seconds faster than the R8."
Despite Audi's status as favourites, they are attempting a remarkable feat in chasing victory with a diesel.
It is a project that would have been considered laughable not long ago because of the extra weight inherent in the engine.
But McNish says he has been impressed by the car.
"The car isn't as nimble or as easy to drive as the R8, although I'm comparing the R10 with a car right at the end of its life," he said.
"What we lose in some areas compared with the R8, we gain in others. We have much more torque, for example."