Toto Wolff says Mercedes could be prepared to accept a one-off compromise in the row over the F1 'engine freeze', but only if it comes with the caveat of long-term assurance that it won't be changed again.

Mercedes has been steadfast on the engine freeze debate throughout 2014 after control costs were implemented with the introduction of the new V6 turbo power units. As it stands, changes to the engine can only be made on the grounds of safety and reliability.

However, having established itself as having the fastest and most reliable power unit on the grid, rivals Renault and Ferrari have spent months applying pressure to Mercedes to agree to a 'thaw' that will give it the chance to make up ground in the interests of the sport.

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Though Mercedes has been reluctant to agree to any changes, the latest from Wolff suggests it will make a one-off compromise, but only if it is assured that the engine freeze will remain in place thereafter.

"If this is the compromise needed to guarantee long-term stability and agree long term we are not going to change the rules every year, that is something we will look at."

Indeed, Wolff says Mercedes has greater concerns about any regulation change beyond its relative dominance in F1, pointing out that it is supplying four teams - including itself - in 2015, whereas Ferrari supplies two, Renault supplies two and the incoming Honda will only focus on McLaren for the time being. As such, it says it has cost implications to take into account.

"They're asking whether it is possible to extend that period and bring another homologation later in the year, probably with a larger scope of possible developments. That means you have a second spec, so you have to do all the dyno running for a second engine that would be introduced.

"You cannot track test it because you are only allowed to use one-spec of engine only, so you have to do all the dyno running and make - in our case - eight powerful and reliable engines. This is going to cost a fortune.

"What we have said is we are calculating what it means financially, what it means logistically because we are a team which needs to deliver eight power units a time, as Honda does two, Ferrari and Renault four.

"So there's a big difference. Once we have gathered all the data over the next couple of days we're going to do that in Sao Paolo."