The FIA has cut off another avenue of potential exploitation with the new Formula 1 engine rules for 2026, offering further evidence that manufacturers have been probing grey areas.

While a major controversy has blown up about potential exploitation of compression ratio limits, a recent change to F1's technical regulations has highlighted that this is not the only place where there has been some uncertainty over what is and is not allowed.

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This second area relates to the fuel-flow meter and comes as a consequence of a completely different way the relevant limits will be imposed for 2026, as F1 switches to fully sustainable fuels.

The previous ceiling, which measured a maximum mass flow of 100kg/h, is being replaced with a fuel energy flow limit of 3000MJ/h.

This significant change has meant a new way of compliance checks being introduced - with the previous use of two fuel-flow meters (one for teams and a control one for the FIA) being replaced by a single standard unit from company Allengra.

This compact, robust, ultrasonic flow meter will be fitted in all cars and will deliver data that is available to both the teams and the FIA.

But while such a standard system would appear to have been a straightforward exercise, a number of minor tweaks to the wording of the rules over recent weeks has suggested that the FIA has been moving to ensure there are no grounds for tricks to be used here.

The issue appears to revolve around teams potentially altering the temperature of the fuel-flow meter.

Doing so could bring benefits either in changing the composition of the fuel that is being measured, or in altering the measurements that the device is taking.

In October, an extra clause was added to the technical regulation that details that cars must be fitted with a fuel-flow meter. It stated that: "Any intentional heating or chilling of the fuel-flow meter is forbidden."

But that wording was subsequently deleted and, after the recent FIA World Motor Sport Council meeting, replaced with a fresh phrase: "Any device, system, or procedure, the purpose of which is to change the temperature of the fuel-flow meter is forbidden."

The change in wording is clearly aimed at being more expansive, and potentially closes off ways that manufacturers could still manipulate the temperature of the fuel-flow meters without it being 'intentional'.

While the more stringent wording has been brought in to prevent any tricks being played, it does not necessarily mean that any teams had been intending to exploit this area themselves.

Often, competitors will air concerns about potential grey areas in the rules to the FIA with the aim of ensuring that all avenues are closed down to stop others jumping on them.

The separate issue of fuel compression, with suspicions surrounding Mercedes and Red Bull of having found a way around the new 16:1 compression ratio limit for 2026, remains ongoing and looks set to be a big talking point ahead of the start of the season.