Sauber will not receive the latest specification of Ferrari engines when its drivers take new power units this weekend.
Both Marcus Ericsson and Felipe Nasr are due to have their fourth and final engine of the year fitted to their cars for this weekend's Russian Grand Prix, but will not benefit from the Monza-spec upgrade Ferrari's works team debuted at the Italian Grand Prix. Instead they will stick with the same specification of engine they used for the first time at the Belgian Grand Prix, which was first rolled out by Ferrari in its own cars as early as the Canadian Grand Prix.
"We are getting a new engine here, but it's the same spec that we have been running," Nasr explained. "We will stick with this one until the end of the year. It's the same spec as we introduced in Spa, so to be honest it should be the same as that."
The Monza-spec engine lacks three tokens-worth of development, but Ericsson played down the impact on performance.
"I think it is what it is and we knew that it was going to be like that for a bit. I don't put much thought into it, I think the update that we had on the last unit was good and as far as I understand the update Ferrari got in Monza was not that big compared to the old one. I haven't really thought that much about it."
Mercedes' customers are in a similar position, with Sergio Perez among the drivers taking a new engine this weekend that is not the same spec as the ones in the cars of Nico Rosberg and Lewis Hamilton.