Some motorists in France are using an illegal method to reduce the price of fuel, which puts them at risk of serious penalties. According to Carbu.com, the average price of diesel is 2.359 euros per liter. Some drivers are willing to pay less for a full tank, even if it involves engaging in illegal activities. In recent days, reports have shown an increase in testimonies from drivers who choose to fill their tanks with non-road diesel, or GNR, which is known as "red" due to its color and is relatively cheaper. An artisan from Lorraine explained that he can obtain GNR for 1.94 euros per liter. Franceinfo found it for 1.72 euros per liter at a gas station on the other side of the Franco-Belgian border, where some residents from the North travel. GNR is so cheap because it is reserved for certain professionals in the agricultural and construction sectors, allowing them to use it in their machines at a lower cost. The government has reduced the taxation of this fuel to economically support these essential sectors. However, it is illegal to use this fuel in a road vehicle, as it constitutes tax fraud. In theory, one must present an official certificate and professional numbers (SIRET for a company, MSA for an agricultural operator) to purchase GNR. Despite this, some motorists manage to obtain it by contacting farmers or presenting jerrycans at a Belgian gas station, where controls are less strict. GNR has characteristics similar to those of conventional diesel, even though its composition is slightly different. It contains less sulfur, a higher cetane index, some additives, and the red coloring that gives it its name. These relatively minor differences in composition mean that a conventional diesel engine can generally run on GNR without immediate mechanical damage. According to a mechanic interviewed by Le Parisien, this is even more true for older vehicles, as older diesel engines have simpler and more tolerant injection systems than more recent ones. Therefore, using GNR will be less risky on a mechanical level in an older vehicle than in a newer one. However, less risky does not mean risk-free. Over time, driving on GNR can still begin to damage the engine. If caught using GNR, one risks a fine of 500 to 1,250 euros in the case of a simple inspection (depending on the amount of fraudulent fuel). Authorities can also confiscate the vehicle. And in cases of serious or repeated fraud, one could face up to three years in prison. The red dye present in GNR is precisely designed to allow police and customs officers to easily detect offenders. This red dye leaves durable traces, especially in the diesel filter. Rather than taking such risks by using GNR, it is better to request government assistance for heavy users if it has not already been done.