Former BMW F1 team boss Mario Theissen has played down suggestions that the German manufacturer may return to the top flight once new technical rules come into force.

Although unable to comment fully on the changes planned for the sport's highest echelon, Theissen admitted that, while the proposed switch to turbo-charged four-cylinder 1600cc forced induction engines for 2013 was a good move, it would not be enough to make BMW reconsider its withdrawal.

"Don't expect that," he insisted to, "When we pulled out, this was a decision for many years, because it takes many years to put something together like this. And the main reason was that we wanted to focus on production car racing instead of formula car racing.

"This is certainly a decision for many years. We are just ramping up our production car programme around the M3 GT2 during the American Le Mans Series and the European 24-hour races, and we are about to decide on a future programme in DTM."

Although other changes to the rulebook are currently being discussed by the various F1 working groups, Theissen agreed that the switch in engine formula was a good one for the sport to make, bringing it more in line with road car thinking.

"I can only really comment on the engine, because I don't know the other proposals," the German admitted, "but, from a manufacturers' perspective, it is the right move to change to innovative technologies that are relevant to road cars.

"If we look at the road car side, we have a conversion right now from high-revving naturally-aspirated engines towards turbo engines with direct injection. So it perfectly makes sense to adapt this concept and maybe combine it with other innovative elements like KERS or something further developed, in order to keep F1 on the edge and probably to be able to be an innovator again for future road car technology.

"Also, I think, current engines are too expensive, so if there is a new set of regulations, it would be a good move to frame the regulations so that design-wise the engine costs will be lower. Of course, F1 has to be the pinnacle of racing and technology has to be on the highest level there, but especially on the engine side, we can do something to get it more affordable."