Fernando Alonso will take a 35-place grid penalty at the Russian Grand Prix after McLaren fitted an upgraded power unit to his car on Friday morning before returning to the previous spec of engine in FP2.

Honda has spent its remaining four tokens on the upgrade and made a strategic decision to run the power unit in FP1 only -- taking a 25-place penalty in the process -- before reverting back to the previous engine. The change back to the previous power unit brought with it a further ten-places in penalties for a new turbocharger and MGU-H and will now be used for the rest of the weekend. The upgraded power unit will then be saved for following rounds where McLaren expects to be more competitive and where it will be able to use it without the need for further penalties.

"We had a couple of extra things to do today," Alonso said. "We had a new engine in FP1 and an old engine in FP2 which had been used in Suzuka with some problems. They were identified and we had to test it anyway in FP2 to be sure that the engine was ready to do the whole weekend.

"So despite the weather we had to go out and calibrate the engine a little bit and everything was working well. It was very positive for us in terms of how the data that we have from the engines is working as we expected. We are ready for the weekend and ready for tomorrow.

"Unfortunately we have this penalty - 35 places. It's not our record because we had 55 in Spa, so let's see how we can manage the race from there. It seems like it could be one-stop for everyone and in which case there is not much of a chance to be creative, so the race could be a little bit more difficult."

A limit on manufacturing time means Honda could only introduce the new power unit on Alonso's car, which was given preference as his previous power unit had more mileage. Team-mate Jenson Button said the important thing was to get mileage on the power unit, but revealed he would have to wait an extra race before being allowed to run the update.

"It's not actually for this weekend as such, the updated engine," he said. "It's for another race, but yes he will have it for that race and I won't. But we need to get it on one of the cars and see what it gives us and mine will follow at the next grand prix after that.

"I think in a team you like to keep it equal but in the position we're in we need to get the engines in the back of the car, we need to do a lot of mileage to see how it is for the future, for next year. So the next few races are going to be testing for us, they're going to be very difficult.

"The only race that I think we could have a chance of doing okay is probably Austin and after that this car is going to be a test bed. We're doing our best to get everything out of the car and to get the best result possible, but simply it will be a lot of testing for us and doing things that maybe you wouldn't normally do in a season with a car and with the engine to make sure we are in the right place for next year."

Roberto Merhi will receive a 20-place grid penalty after Manor installed the fifth internal combustion engine, turbocharger and MGU-H of the season on his car.