The FIA has closed a loophole for 2017 which allowed drivers to stockpile engine components, therefore circumnavigating the engine penalty rules which stipulate that for each new component used, a driver must take a grid penalty.
The loophole was used successfully by McLaren last year and by Mercedes driver Lewis Hamilton earlier this season in Spa. The Briton suffered poor reliability during the early races and was already on his final allocated power unit come the Belgian Grand Prix.
In order to make it to the end of the season without taking more penalties, Mercedes installed three new engines in Hamilton's car during the weekend. Although that forced him to start from the back of the grid, it meant he had three new engines for the remaining rounds.
That has been banned for 2017, with the World Motor Sport Council agreeing that only the very final component (or entire unit) installed during a race weekend can be used at future events.
"During any single event, if a driver introduces more than one of a power unit element that is subject to penalty, only the last element fitted may be used at subsequent events without further penaltym," confirmed a statement.
"This is to prevent the stockpiling of spare power unit elements."
