Engine-related grid penalties have been a hot topic in recent weeks, given their potential impact on the 2021 title fight.
For 2021, teams are allowed to use three Internal Combustion Engines, three Turbochargers, three MGU-Hs, three MGU-Ks, two Energy Stores, two Control Electronics and eight Exhausts per car without incurring a penalty.
Red Bull driver Max Verstappen moved on to his fourth Honda power unit in Russia last time out but recovered from the back-of-the-grid to finish second to Lewis Hamilton, who has yet to move beyond a third Mercedes engine.
Mercedes boss Toto Wolff has admitted that Hamilton taking on a fresh engine, and a subsequent grid penalty, is a "possibility" at this weekend's Turkish Grand Prix, though he added: "When, and how, is not yet decided."
Hamilton himself said: "I don't envision us having to take one at the moment, but that could change."
As the F1 paddock reconvenes at Istanbul Park, Hamilton is one of several drivers on the brink of an engine-related penalty, as can be seen in the full list below, detailing the power unit elements used so far this season.
Carlos Sainz's recently confirmed engine change is not included on the list, as the Ferrari driver has yet to complete any mileage with his new unit.
Lewis Hamilton claimed his 100th Grand Prix win to move into the championship lead, but it's Red Bull and Max Verstappen who will be happiest after the Russian Grand Prix.