The new Honda and Renault power units are already more powerful than last year's Ferrari engine, according to Paddy Lowe.
Last year saw a clear split in the field with Ferrari closing the gap to the dominant Mercedes power unit, while Renault and Honda struggled with both power and reliability.
This season, Toro Rosso is running a year-old Ferrari power unit, with the team using the latest specification of engine from 2015. Despite strong results and Toro Rosso praising the improvement with the Ferrari offering, Mercedes' data shows Honda and Renault have already moved ahead.
"You may not know this, but the engine with the least power on the grid is actually the Ferrari in the Toro Rosso," Mercedes technical boss Paddy Lowe told ESPN. "The Renault and the Honda are not so far behind the Ferrari and Mercedes, so there is not a lot of difference now between the power units."
Max Verstappen finished sixth for Toro Rosso in Bahrain, highlighting the strengths of the chassis. Verstappen himself said during the race weekend that Red Bull's Renault power unit has improved markedly over the winter.
"To be honest I'm not really surprised," Verstappen said when asked about Red Bull's performance on a power-sensitive track in Bahrain. "They have a great car, I knew that already. With the engine they made a big step forward."
Scene at the Bahrain Grand Prix
Bahrain Grand Prix - Quotes of the weekend
DRIVER RATINGS: Bahrain Grand Prix
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