Formula 1 circuits have asked the sport's bosses for reassurance that the switch to V6 turbo engines in 2014 will not be a turn off for fans - amid fears that it could hurt track profits.
Silverstone managing director Richard Phillips says that circuits are concerned that a minority of fans could turn their backs on F1 if the new power units detract from the sport's spectacle - even though senior engineers are adamant the new engines will be just as impressive as the current ones.
When asked by AUTOSPORT about how genuine the circuit worries were, Phillips said: "Our concern is because we have taken on a 17-year deal, which it is not a cheap thing to do. You have a big crowd coming at the moment, but what if they don't like 1600cc engines and 15,000 rpm? It only takes 10,000 - 15,000 people not to come and it makes a huge difference. That is where we make our money; it is the top end of it.
"So we are objecting because of that. We also think that the footprint of the racing is not much of an issue from a carbon footprint point of view. It is probably more the travel and other things that are far greater and they are not really addressing that."
Although talk that circuits would opt to ditch F1 in favour of IndyCar has been viewed with scepticism - especially because IndyCar is also switching to turbo V6s - Phillips says that the main issue is that the tracks should be consulted about issues that could affect their audience.
"If we were consulted and re-assured that these things will not be an issue, and we felt consulted, then I don't think we would have such an issue," he explained. "But to have it forced upon you? We live with the commercial ramifications of it, they don't. We are not disagreeing; We are all up for greener motorsport and doing what we can...
"I have no problem with the green agenda. We are so close to being a fence sitter on this, but we are just worried about the crowd. If that did go wrong, we know it is right at the minute, but to say, 'yes that is absolutely fine' and then it turned out not to be: that would be very serious as a promoter."
Read more about the race promoters' worries in the Weekly Grapevine.