Despite an early season move to better measure fuel-flow rates, the governing body is still not satisfied that the situation is under control.

It has been suggested that some teams could be gaining an advantage through clever engine management settings that boost fuel-flow rates for short periods of time – which could be of particular advantage in qualifying.

There have been some claims that Mercedes and Ferrari have been exploiting this area to varying degrees since the start of the campaign – although neither team has broken the rules.

Hot topic refuses to go away

The controversy over fuel-flow rates originally prompted the FIA to issue a directive stating that from the Chinese Grand Prix onwards, fuel pressure measurements would be taken at multiple points.

Sources suggest that the matter of fuel-flow rates came up again at a meeting of technical directors earlier this week, and the FIA has now issued a note to teams making it clear that there are new limits in terms of what teams can do.

Whiting issues new directive

In the note sent on Saturday by F1 race director Charlie Whiting, a copy of which has been seen by Motorsport.com, he has made it clear that teams will no longer be allowed to vary their fuel-flow rate.

“With immediate effect we will expect fuel pressure, in the high and low pressure systems, to remain constant above a flow rate of 90kg/hr,” wrote Whiting.

“We do not consider it necessary to define here what we consider constant, we feel it will be more practical to discuss any concerns we have with the relevant team(s) if and when issues arise.”

Whiting also indicated that the FIA would be moving to individually check out each of the teams' fuel systems to ensure that there was full compliance with the regulations.

“We will also be carrying out careful physical inspections of all fuel systems in use,” he said.