Mercedes has confirmed it has spent five development tokens on upgrading its power unit ahead of the Belgian Grand Prix this weekend.
Mercedes drivers Lewis Hamilton and Nico Rosberg will use the new units this weekend, they won't however be available to customer teams Williams, Force India and Manor until the next race at Monza.
The team hasn't confirmed which components it has spent the tokens on.
The upgrade means Mercedes now has just six remaining, three more than Honda and Ferrari, whilst Renault have 21 remaining, having spent just 11 so far this season.
Championship leader Hamilton will start Sunday's race from the back of the grid after Mercedes opted to take two fresh units this weekend, with each incurring a separate 15-place grid drop. He will therefore drop 30 places in total, with McLaren's Fernando Alonso dropping 35 and Sauber's Marcus Ericsson 10.
