1. Tax first, then the market: what actually makes the gap
In most of Europe the tax system favours diesel. Germany charges 47.04 cents of energy tax per litre of diesel against 65.45 cents on petrol, a difference of 18.4 cents net or about 22 cents with VAT (Energy Tax Act). When diesel nevertheless costs 16.3 cents more at the pump, as on 17 September 2026 (ADAC), the market price of diesel sits roughly 38 cents gross or over 30 cents net above petrol. The gap is not made at the forecourt or by the tax office; it is made between the refinery and the depot.
It has not always been like this. In normal years German diesel costs less than petrol because of the tax advantage; the last time it cost more was autumn 2022, when Russian diesel exports disappeared. In the United States there is no tax preference for diesel, which is one reason the American gap is the widest of the four countries. Germany's fuel tax cut from 1 October will not change the gap, because it lowers both fuels by the same amount (see Germany's fuel tax cut).
2. The three reasons
First, the refining margin. A refinery turns a barrel of crude into a fixed bundle of petrol, diesel, jet fuel and residual oil, and the shares can only be shifted within narrow limits. When diesel is scarce, its price rises above petrol without any more diesel being made. On 22 September 2026 ICE gasoil cost $1,452.50 a tonne, about $195 a barrel at the customary factor of 7.45, against $99.80 for Brent (HeizOel24.at, 19:40). That gap, the diesel crack spread, is roughly $95 a barrel, or over 50 euro cents a litre before tax and distribution.
Second, supply. Russia, Europe's largest diesel supplier before 2022, has extended its export ban on diesel, petrol and jet fuel to the end of October after drone strikes forced three of its six largest diesel refineries to cut or halt output in September (Hydrocarbon Processing, 16 September). The Gulf states export finished products, and their product shipments through Hormuz are recovering more slowly than crude (Bloomberg, 10 September). Petrol is less affected: the United States, the biggest petrol market, makes its own, and US gasoline stocks of 207.7 million barrels in the week to 11 September were far more comfortable than distillate stocks of 107.9 million (DOE via HeizOel24).
Third, demand. Diesel moves trucks, ships, farm machinery and construction sites and is chemically the same as heating oil; in autumn the heating season comes on top. Petrol peaks in summer and fades in autumn. That the gap is setting records right now is partly a matter of the calendar.
3. Four countries, one pattern
| Country | Diesel | Petrol | Gap | Date, source |
|---|---|---|---|---|
| United States | $6.53/gal | $4.48/gal (regular) | +$2.05 (+46 %) | 22 Sep 2026, AAA |
| Germany | €2.471/L | €2.308/L (E10) | +16.3 ct | 17 Sep 2026, ADAC |
| France | €2.41/L | €2.17/L (SP95) | +24 ct | 20 Sep 2026, Hérault Tribune |
| Spain (with rebates) | €1.829/L | €1.867/L (95) | −3.8 ct | 22 Sep 2026, Motor16 |
| Spain (without rebates, arithmetic) | €2.071/L | €1.928/L | +14.3 ct | our calculation: +20 and +5 ct tax plus 21 % VAT (Motor16) on the 22 Sep 2026 prices |
Spain shows how much policy distorts the picture: diesel is still cheaper than petrol at Spanish pumps, but only because the state has subsidised diesel by 20 cents and petrol by 5 cents since 1 September (El Español). If the rebate expires on 30 September, the sign flips; Motor16 expects up to 24 cents on 1 October. The UK picture is on UK petrol and diesel prices forecast.
4. When does the gap close again?
The EIA expects a US gap of $1.60 a gallon in the fourth quarter of 2026 (diesel $5.55, petrol $3.95) and $1.05 in 2027 ($4.40 against $3.35), smaller but still unusually wide (STEO, 9 September 2026). The condition is a normalisation of Hormuz in the second quarter of 2027 and a rebuilding of distillate stocks, which the EIA expects to stay below the five-year low through much of 2027.
Europe has no comparable official forecast. Three things would close the gap faster: Russian refineries return and the export ban falls; Gulf product shipments normalise after a reopening of the strait (see Hormuz reopening: three scenarios); and winter ends. Until then, anyone choosing between a diesel and a petrol car should budget with today's gap, not 2019's. More on the shortage itself on Diesel shortage winter 2026/27.
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