Formula 1 teams are unlikely to get a fifth engine in 2015 unless the Korean Grand Prix stays on the calendar for the start of the season, the FIA suggests.
The return of the Korean GP caused a surprise on Wednesday, when the FIA's World Motor Sport Council ratified a 21-race schedule that had been provided to it by Bernie Ecclestone.
With organisers in Mokpo expressing shock at the decision, and plans for a street race in Seoul still far from being ready, there has been speculation about why Ecclestone has been so keen to slot the race in.
One theory is that the decision to add another race beyond the 20 approved by the FIA in September is that it would open the door for teams to be allowed to use a fifth power unit.
Under the current F1 regulations, each driver is limited to just four power units for the entire campaign if the number of races does not exceed 20.
However, there is a clause that allows the use of a fifth engine if there are more races.
Article 28.4 a) of Formula 1's Sporting Regulations states that drivers are limited to four power units for the season.
However, it adds: "This number will be increased to five if the number of Events in the Championship, as originally scheduled, exceeds 20."
The use of the phrase 'originally scheduled' has been interpreted by some as meaning that if there are 21 races down provisionally, then even if one drops off then that is enough for teams to be given the extra engine.
However, senior sources at the FIA insist that such an interpretation of the regulation is unlikely to stand.
The scheduling of the race, which is pencilled in for May, means that its slot in the calendar will need to be finalised before the season begins in Australia.
With a provisional 2015 F1 calendar having been published by the FIA in September, and a final version therefore needing to be sorted before the first race, it will be hard for anyone to argue that the Korean GP was 'originally scheduled' if it drops off.
The only way that teams will be guaranteed the fifth engine will be for the 21st race to be on the official schedule when the campaign begins in Australia, for by then teams will have finalised the lifing of their power units.
Teams faced a spate of reliability problems this year, when they had five engines for the 19 races, so there are worries that the situation could be even worse in 2015 when they have four engines for 20 events.
That is why any chance of getting an extra power unit would be a bonus.
The potential opening for a fifth engine may, however, be used by Ecclestone as a tool to get support from teams for an extra race somewhere else next year - even if Korea does not happen.