Sebastian Vettel ended a hot opening practice session from the German Grand Prix weekend on top of the timesheets.
Temperatures at the Hockheimring read well over 30 degrees Celcius during the session and it is expected that it will only rise as the afternoon wears on and the second practice session gets underway later today.
Ferrari seemed to be much more hooked up to the circuit, as Mercedes struggled for grip during their hot laps, with both Lewis Hamilton and Valtteri Bottas going off the circuit at the final corner.
Bottas found himself in the gravel at Turn 12 in the final minutes of the session after locking up the front left tyre. However, the Finn was able to stop the car in time and recover onto the circuit on his own.
Hamilton ended the session in third place, three-tenths down on Vettel, but only marginally behind Charles Leclerc, who was second for Ferrari.
Max Verstappen managed to split the two Mercedes as Red Bull eyes further improvements this weekend, following on from a couple of events in which it has been able to challenge Ferrari.
Bottas was fifth, ahead of Pierre Gasly who was half a second down on teammate Verstappen.
McLaren split its programme between its two drivers, with Carlos Sainz topping the midfield pack ahead of Romain Grosjean in the Haas.
Grosjean is once again running the Australia-spec VF-19 this weekend, which has initially proven to be the better package, as he was seven-tenths ahead of teammate Kevin Magnussen.
Magnussen caused the one and only red flag of the session, as he stopped on the circuit early on with a reported sensor issue. The Dane was towed back to the pit lane and was quickly back out onto the circuit.
Lance Stroll was ninth for Racing Point, who has brought a big upgrade to the German Grand Prix, while Daniel Ricciardo rounded out the top ten - despite a spin at Turn 1 late on in the 90-minute session.
Traffic was an issue for a number of drivers throughout the session, with a number of drivers getting held up through the fast Turn 11 right-hand corner.
The second practice session will get underway at 3 PM local time - however the session is set to bring extremely high temperatures, which could make for an unrepresentative session.