Why didn't Mercedes use Lewis Hamilton's fresh "Brazil" engine at Qatar GP?

Mercedes' trackside engineering director Andrew Shovlin explained the need to use an older engine in Lewis Hamilton’s car at the Qatar GP. Hamilton still managed to set the pace comfortably, winning both pole and the race by hefty margins.

In the team's race debrief, Shovlin explained the strategic philosophy behind saving the new engine from the Brazil GP for the last two races on the calendar, by saying:

“It wasn’t the engine the fresh one that we took in Brazil, this was an older engine, and because it is an older engine, it's got a bit less power. [Among] the remaining circuits, Qatar has got the shortest amount of straight-line, the shortest amount of full throttle running, and has got an awful lot of cornering. The power advantage you get at Qatar is much smaller than you get at the two remaining circuits.”

Shovlin explains Lewis Hamilton's engine decision in this video (from 7:15 onwards):

In Brazil, Hamilton’s car had been fitted with a brand new engine which gave him a performance advantage over the rest of the field in the sprint race, qualifying session, and the main race. According to the Mercedes engineer, it was critical to strategize the use of that engine and carry its performance advantage to circuits where it would be more beneficial.

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Mercedes to use Brazil engine in last two races

Describing Mercedes' philosophy behind strategizing their engine usage, Shovlin said:

“So all we are doing really is trying to balance the mileage across the pool. [To] make sure that when we use the less-powerful engine, there is less of a penalty for it. And that also means that when we get to the final two tracks, we can have the most power that we possibly can."

After the Brazil GP, Shovlin also explained how Hamilton could not be overtaken due to the one-race performance delta he had in the race. With the straights peppering the Jeddah Corniche Circuit layout, switching back to the new engine will be beneficial for Hamilton.

In Abu Dhabi, on the other hand, where track position will be key, the new engine could be beneficial in qualifying. However, with one out of two circuits being a new one, it is uncertain how significant that performance advantage will be in terms of straight-line speed, as it will depend on whether Red Bull F1 bring a chassis update to counter their pace deficit.