McLaren recruit Oscar Piastri has identified the differences between Mercedes and Renault power.
The Australian, however, has warned it is too early to assess a complete comparison due to the run plans of other teams at the recent Abu Dhabi post-season test.
Piastri made his McLaren bow at the Yas Island circuit ahead of his rookie season next year after making the switch from the Woking-based outfit's rivals for fourth in the constructors' championship this past campaign in Alpine.
As part of his preparation for what was projected to be his step into F1 with the French manufacturer, Piastri completed a number of test days in old machinery.
That was designed to get to grips with the operational side of the sport, during which the former F2 champion would have experienced Renault's power unit offering.
Asked what he thought of McLaren's Mercedes engine, Piastri replied: "I thought it felt good.
"There are a few differences to the Alpine engine I drove in the '21 car.
"But being able to compare with other cars on track is a little difficult and the main aim was not to assess where the engine is at.
"You never know where everyone's engine settings are, so it is hard to get a read on that but everything felt positive on our side."
Casting judgment on the 18-inch Pirelli prototype tyres, Piastri added: "The cars themselves are also so different in quite a few aspects that again it is quite hard to say.
"The [Alpine] academy tyres are probably a bit more user-friendly in some conditions but probably harder in others.
"It was a bit hard to get a read but the tyres I drove, I don't really know any different to the 18-inch F1 tyres.
"They stayed on the car and kept me going around so they seemed fine."