Red diesel is widely used in France, but the government are tightening controls on its use.

The terms ' 'fioul', 'gazole' as well as the English words 'diesel' and 'fuel', are all used in France to describe diesel products. In some parts of the country, you may also see the term 'mazout' used.

Although all these terms are used interchangeably, 'fioul' usually refers to domestic or light industrial heating oil of a type used in boilers, whilst 'gazole' is most commonly used in the context of both on and off-road vehicles and marine use.

Nevertheless, the terms relate to identical or very similar products, with only minor differences between them. Thus, fioul has a higher calorific value than gazole – which is why it is particularly suitable for heating.

In the past, heating and agricultural diesel were widely used interchangeably, with heating fuel used for off-road agricultural and construction machinery, as well as some boats – and vice-versa.

In 2011, European legislation was introduced limiting the maximum sulphur levels permissible in agricultural vehicle emissions. That required the development of a new diesel product which in turn meant an eventual technical segmentation between heating fuel and that used by agricultural and other off-road use vehicles.

Those changes, plus other technical differences introduced by way of additives since, have led to today’s position where diesel in France is typically described as being either:

• Fioul domestique - used for domestic/smaller commercial heating, either ordinaire/supérieur, with the latter containing special additives designed to improve the economic performance of a boiler or poêle, reduce some emissions and deliver clean-as-it-goes benefits;
• Gazole Non-Routier (GNR) - off-road fuel. This is (theoretically) only used by agricultural or off-road construction machinery. It may also be used by pleasure boats and craft sailing in French inland/coastal waters, such as barges;
• Gazole - standard road diesel used by ordinary on-road vehicles.

Very broadly speaking, in technical terms, the above products are roughly interchangeable. For example fioul can be used satisfactorily in agricultural vehicles; GNR can typically be used in domestic boilers, though perhaps with some loss of efficiency; Fioul/GNR can be used in a typical car or van on the public highway, particularly in older vehicles, although potentially with an adverse impact on parts such as filters and injectors.

Users of both fioul domestique and GNR pay a significantly lower price per litre than ordinary road users purchasing gazole, due to reduced duties and taxes. That is largely to do with efforts to subsidise the agricultural and construction industries, as well as offering assistance to householders heating their properties during winter.

The price of a litre of domestic fioul ordinaire is approximately €0.94. The price for a litre of GNR is €0.97. By contrast, a litre of standard gazole costs around €1.48. Similar differentials are applied across Europe.

These price differences are a major temptation for many road users, and the practice of running a private road vehicle on red diesel is assumed by the authorities to be far from rare. The rural nature of large parts of the country means discussion about 'rouler au rouge' can be heard frequently amongst locals and expats alike.

As a result, the government goes to substantial efforts to reduce abuse.

In order to help identify it specifically and thereby reduce the instances of lower-cost diesel being used in ordinary cars, as elsewhere in Europe, a red dye is introduced to fioul/GNR and some chemical trace markers likewise

Petrol stations are required to complete a form that includes the name and address on the person buying GNR at the pump.

The police and gendarmes in conjunction with customs officials will periodically stop vehicles for random control checks, which may include tests of the fuel in the vehicle’s tank. Stops and fuel tests are more commonplace today than was the case in the past.

Public road driving on red diesel is a serious offence under custom duty evasion laws and is charged as tax fraud. The penalties can be severe, including a very large fine, potentially three years in prison and confiscation of the vehicle.

In 2018, the government announced that GNR would be phased out for construction industry users, although not for agricultural use.

The changes were planned to start in July 2020 and to be fully phased-in by January 2022. This was anticipated to raise between €600-€900 million in taxes.

Predictably, this led to fury, with opponents claiming it was effectively a 50% increase in their fuel costs. It was a factor in the 'gilets jaunes' public unrest in 2018 and, along with several other controversial measures, the government quickly abandoned it.

However, the plan was quietly re-introduced in early 2019 leading to more public demonstrations and the blocking of major refineries in the north and north-west by construction vehicles. There were moderately widespread fuel shortages as a result in much of northern, western and central France.

In early 2020, the protests appear to have subsided and it is assumed that red diesel use after 2022 will be restricted to agricultural and domestic heating users – though that might be changed by events.