Ferrari may now have the most powerful engine in formula one.
For the whole of the ’power unit’ era since 2014, Mercedes has clearly led the way and won every world championship.
But Auto Motor und Sport claims that Ferrari has caught up in 2018.
"GPS measurements show that in terms of engine performance, Ferrari has caught up with Mercedes," the report said.
"Mercedes increased mileage from 5,000 to 8,000 kilometres (per engine), but Ferrari found even more power over the winter," Auto Motor und Sport added.
Sebastian Vettel confirmed: "On the straights, we’re not losing time to Mercedes."
The German magazine claims Mercedes this year went back to an oil specification that it used in 2016, as the FIA clamped down on a rule about oil consumption.
Boss Toto Wolff said: "The measurements are not precise, so if you’re on the limit, you risk sometimes going over it."
Auto Motor und Sport, however, said Ferrari is pushing ahead with a "full risk" strategy regarding the oil consumption rule.