Some might be forecasting a straight, no-holds barred duel between diesel heavyweights Audi and Peugeot in this weekend's 77th edition of the iconic Le Mans 24 Hours, but defending race-winner Allan McNish has warned that only a fool would discount the threat from petrol front-runners Aston Martin, Pescarolo and Oreca as well.

A petrol car has not prevailed in the legendary round-the-clock La Sarthe classic since 2005, when the Audi R8 achieved its final victory in the event before making way for the revolutionary R10 TDi. That model too has now been replaced for this year by the R15 TDi, which McNish contends is a step further forward still [see separate story - click here] - a statement sure to strike fear into the hearts of the opposition, with the Ingolstadt manufacturer having been defeated just once in the past nine years, by Bentley with its Speed 8 back in 2003.

This time around, Peugeot is determined to turn the tables on its German rival on home turf, having returned to Le Mans in 2007 and boasting arguably the fastest car ever since in the shape of the 908 HDi, but having thus far been unable to produce the necessary consistency over 24 hours to pull off the ultimate result. McNish suggests the addition to the squad of David Brabham - runner-up in 2003 in the second of the two British Racing Green Bentleys alongside Johnny Herbert and Mark Blundell - could just be the final missing piece of the puzzle for the Lion.

"I think 'Brabs' brings stability to them," the Scot contended, speaking exclusively to Radio ahead of the big race, "and they have definitely got a better structure than they had last year - we saw that at Sebring in the way they ran the race. In fact, they had a guy sitting opposite our pit box, who every time our car came into the pits was picking up his video-camera.

"I think they've copied Audi in the way they do things, which is I suppose a nice compliment to Team Joest that the might of Peugeot feel they have to video us to watch what we're doing - but on the back of the video they get a smiling Allan McNish waving at them every time, so I hope that gave them some entertainment when they were watching it back!

"They have developed and have got Brabs involved, and I think the car that he's in with [Alex] Wurz and [Marc] Gen? is probably their strongest car in a way, because it's a very intelligent driving crew and they've all been successful in the past, so I would certainly see the threat coming from them through the end of the race.

"The Montagny/Sarrazin/Bourdais car is probably quickest in terms of outright, one-lap speed, but there's more than one lap to winning Le Mans. The other car has Minassian in, and Nic is one of the best sportscar drivers around, but as we all know it's a package of driver and car and team that wins Le Mans."

Beyond Peugeot, the challenge looks to be three-fold, with Aston Martin's return to the front end of competition in the LMP1 class - poignantly on the 50th anniversary of the esteemed British marque's first and thus far only triumph back in 1959 - allied to the home-grown efforts of Pescarolo and Oreca, all of whom McNish tips to stick the odd thorn or two into Audi and Peugeot's side as the race wears on.

"I see Aston Martin being very strong," the 39-year-old underlined, "because if you take the facts of life, they were already ahead of one of our R10s last year, and since then we've had restrictions on our refuelling, we've had restrictions on our power output and we've had 30 kilos added. All of those are negative to our performance, whilst they have developed the car forward from there.

"They won the first Le Mans Series race in Barcelona, and they had the fastest top speed of anyone - including Peugeot - at Spa, so you have to say that if they bring that to Le Mans they're going to be very competitive. Putting [Jos] Verstappen, Anthony Davidson and Darren Turner all in one car tells me that they're not just going there for a Sunday afternoon drive.

"I think the fastest petrol car over one lap by what the journalists are saying is actually the Pescarolo; however, from a driver line-up point-of-view, I would say the main drivers that Pesca have got are in the Peugeot. That certainly does affect where they're putting their emphasis, but there's no way you can discount Henri at Le Mans. He is a guy that ran a very privateer outfit nearly to victory in 2005, and now I think he's got much more armoury at his disposal.

"With regard to the Oreca, Hugues de Chaunac has won Le Mans outright before when he was running a manufacturer programme, he's won it in category with the Dodge Vipers and I've raced for him and I think he's one of the best. He's put together a very good driver crew and the aerodynamic set-up on that new Oreca is very efficient, and they would have finished on the podium quite easily on the car's first run out in Spa, so yes, they will be a threat as well - there's no way you can discount Hugues at Le Mans either.

"It's not just a fight between the three marques that people automatically think of. I think there are other people that will come into play at different points in the race - not necessarily on the first lap, but as we talked about before, there are a lot more laps than just that to win Le Mans."