"This (Jerez) was purely an engine test, so the teams had the chance to try the new engines," former triple world champion Lauda told Osterreich newspaper.
"We drove three and a half grand prix distances and I am very satisfied," he said.
"At the moment it looks as though we have the edge, but that could change very quickly," Lauda warned.
He said he sympathises with Red Bull, who struggled even to run the new Renault-powered RB10.
"The new, hybrid engines are very sensitive and complex and not easy to get to grips with," said Lauda.
"Technically, it's an enormous challenge and also at Mercedes we had many small problems, but we were able to solve them immediately," he added.
Lauda recently scolded Bernie Ecclestone for criticising F1's new, 'greener' era, and now he says the Briton is also wrong to complain about the sound of the V6 engines.
"The engine noise is just as attractive as before," he insisted.
Lauda isn't even bothered about the 'ugly' noses of 2014, insisting: "Once a car is quick and it wins, it is also beautiful."
Meanwhile, the Austrian great has slammed a German magazine called Titanic, who in the latest edition put Lauda's scarred face on the cover with the headline: "First photo -- this is how badly Schumi's accident affected him".
Lauda told Haute newspaper: "It's impertinent, disrespectful and absolutely unacceptable. Who would print such rubbish?"
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