At the back of a garage, near the workbench, a float gauge shows half a tank of fuel. This autumn, the gauge often stops there. Domestic fuel now costs around 1.85 euros per liter, and prices have risen by more than 60 percent since January. Filling a 1,000-liter tank now costs nearly 1,900 euros, prompting many to order only 500 liters at a time and pay in installments, waiting to see what happens in February. Fuel distributors have noticed this trend, describing a significant drop in orders. Though the gesture may seem minor, it is one of the most reliable social indicators in the country. The fuel tank, in essence, tells a story that households might not yet be willing to admit in surveys. According to Insee, France's national statistics institute, 2.6 million primary residences are still heated with fuel oil, accounting for 8.5 percent of the housing stock. This average, however, hides regional disparities. Fuel oil heats 16.7 percent of rural housing, compared to just 3.5 percent in densely populated cities. In many rural communes in the Massif Central, the Alps, or northern France, the proportion of homes using fuel oil exceeds 30 percent. In Lozère, where gas networks are nearly non-existent, more than one in three homes relies on fuel oil. The profile of those who use fuel oil is also clear. These are often long-term homeowners, many of them elderly. In 2022, people aged 75 or older made up 30 percent of fuel oil users. Their homes are typically large, old, and poorly insulated. More than half have energy efficiency labels E, F, or G, indicating significant inefficiency. In 2021, Insee estimated that the average annual heating bill for these households was 2,900 euros, compared to 1,700 euros for other households. Nearly half of these households were in a state of energy vulnerability before the current price surge. The reliance on fuel oil is a historical paradox. In 1973, half of French homes were heated with fuel oil, a symbol of modern comfort during the post-war "Glorious Thirty" era, marking the end of coal and wood heating. Fifty years later, this progress has turned into a burden. Those who once embraced fuel oil as a modern convenience are now the last to be able to move away from it. Many are trapped by an outdated system, but the government has taken action. Since July 2022, the installation of new fuel oil boilers has been banned, except in rare cases. Financial aid for switching to more modern heating systems has increased. Between 2006 and 2022, the number of homes using fuel oil has nearly halved. However, the decline has been more pronounced in areas with growing populations and frequent construction and relocation. In regions like the Creuse, the Cantal, or the Haute-Marne, the decline has been much slower, with heating changes happening more slowly through inheritances than through new installations. Switching heating systems requires two resources that many of these households lack: money and time. At 80 years old, in a house that has become too large and where only two rooms are heated, the math is clear. Many choose to keep their old boilers and monitor the fuel gauge closely. These households have no financial cushion. The 2022 winter fuel check, which provided temporary relief, was not renewed, and only the standard energy check remains. By late September, the government renewed its aid for motorists who drive a lot, but no similar support exists for fuel oil users at this stage. These households bear the brunt of a market affected by geopolitical tensions in the Middle East and uncertainties in river transport on the Rhine. For them, geopolitics is not a news story—it’s a line on their bank statements. France, however, is aware of the cost of neglecting these regions. The anger of 2018 stemmed from a rise in fuel taxes, where a car is a necessity. The fuel tank operates on the same logic of dependence. It is simply more discreet, often hidden at the back of a garden or in a basement. The thermometer, therefore, is present in over two million households, measuring the temperature of a country that heats itself, without a network and without a safety net. It remains to be seen whether someone in Paris will pay attention to it before winter.