Brent fell 16% in a week, and petrol gave back 1.3p a litre

Brent crude was heading for a 16% fall in the week to 6 November, the steepest weekly drop since the start of the pandemic and the largest in absolute terms in LSEG data going back to 1988 (Business Recorder, 6 November). The last official pump reading before that run of trading, for the week beginning 2 November, put petrol at 172.78p a litre and diesel at 198.58p (DESNZ, 3 November).

That is 1.3p and 0.6p below the week before. Against a crude move of this size, it is almost nothing.

What the oil market did

The trigger was the US midterm elections. As the Democrats took control of Congress, traders read a higher chance of an end to the war with Iran and marked crude down 8% on Wednesday 4 November alone, taking Brent below $95 a barrel for the first time in two months (Visordown, 6 November).

Prices then rebounded as attacks on tankers in the Gulf and the Strait of Hormuz resumed. Brent's January contract was up 0.3% at $98.60 a barrel by late morning on Friday 6 November, still on course for a weekly fall of about 16%. West Texas Intermediate was heading for a 13% weekly decline (Business Recorder, 6 November).

Brent had closed at $117.64 on 30 October, so the week took roughly a fifth off the benchmark at its low point before the rebound. A barrel of crude is not a litre of fuel, and the gap between the two prices has several stages to cross before it reaches a forecourt.

What reached the forecourt

The Department for Energy Security and Net Zero publishes a weekly average, and the recent run shows how little of the move has arrived:

week beginning 12 October: petrol 175.28p, diesel 200.04p
week beginning 19 October: petrol 174.57p, diesel 199.33p
week beginning 26 October: petrol 174.07p, diesel 199.22p
week beginning 2 November: petrol 172.78p, diesel 198.58p

Over those three weeks petrol fell 2.5p and diesel 1.46p. Most of that happened before the midterm result.

Daily readings from PetrolPrices.co.uk put petrol at about 170.6p and diesel at 198.3p on Friday 6 November (Visordown, 6 November). Against the 172.78p average for the week beginning 2 November, that is 2.2p lower for petrol and 0.3p lower for diesel.

The diesel number is the interesting one. Diesel sits in a tighter global market, where the threat of a US export ban has been hanging over supply (RAC, 2 October). It reached a record 200.04p in the week beginning 12 October. Three weeks of falling crude have taken 1.46p off it.

Why a barrel is not a litre

Refining, shipping, biofuel blending and the exchange rate all sit between crude and the pump. The wholesale price of finished petrol and diesel moves with refining capacity and demand as well as with crude, and both fuels are traded in dollars, so a weaker pound can eat into a fall in the oil price (RAC Fuel Watch).

There is also a time lag. The RAC puts the typical delay between a wholesale move and the forecourt at about two weeks (Visordown, 6 November). A station sells fuel it bought days or weeks earlier, so its replacement cost can be falling while the price on the pole stays where it was.

The RAC's Simon Williams said in September that only a sustained lower oil price, over several weeks rather than days, would lead to cheaper prices at the pumps (RAC, 28 September). A week of sharp falls in crude does not meet that test on its own, and this one has already partly reversed.

What a full pass-through is worth

Two taxes sit inside every litre. Fuel duty is fixed at 52.95p and does not move with the oil price. VAT is 20% on the total, including the duty (DESNZ weekly road fuel prices).

At 172.78p, petrol carries 28.80p of VAT on top of the 52.95p duty, so 81.75p of the litre, or 47%, goes to the Treasury. At 198.58p, diesel carries 33.10p of VAT and 86.05p in total tax, or 43% of the price.

VAT is proportional, so a fall in the wholesale price is magnified at the pump. Take 10p off the pre-VAT cost of a litre and a retailer passing it all through would cut 12p from the price. On a 55-litre tank that is £6.60. A driver covering 10,000 miles at 45mpg uses about 1,010 litres a year, so the same 10p wholesale fall would be worth about £121 over 12 months.

That arithmetic cuts both ways, and it explains why the tax share is higher on petrol today than it was at the 2022 peak. The duty is a fixed number of pence, so it takes a larger share of a cheaper litre.

What happened the last time crude fell

The June series is the closest recent test. Between the weeks beginning 1 June and 29 June, petrol fell from 158.74p to 151.02p and diesel from 184.11p to 167.12p (DESNZ). Diesel lost 17p in four weeks, petrol 7.7p.

The fall took a month to work through, not a week. It is the pattern the RAC describes: a lower oil price has to persist before it shows up in force at the pump.

FairFuelUK has started its own clock. "Oil has crashed. So the clock starts now," the campaign group's founder Howard Cox said, and the group plans to check prices at 7, 14, 21 and 28 days (Visordown, 6 November). It is also renewing its call for a PumpWatch system that would provide transparency over wholesale costs, retailer margins and pump prices.

What it means for a driver

The practical answer for anyone with an empty tank is to fill up as normal. Waiting a week in the hope of a 5p fall risks running dry to save about £2.75 on a 55-litre fill.

The bigger sums are on the annual bill. Diesel at 198.58p and the 45mpg the RAC uses for an average diesel car costs 20.1p a mile, so 10,000 miles comes to £2,006. Petrol at 172.78p and the same economy costs 17.5p a mile, or £1,746. Four weeks at the June pace of decline would take about 17p off diesel, worth roughly £170 a year to that driver, if crude stayed low.

The comparison that does not move with Brent is the one that has changed most this year. An electric car charged at home on Octopus's 6.6p overnight rate costs about 2p a mile, or £200 over 10,000 miles (our guide to the home charging rates). Diesel at 20.1p a mile costs ten times as much.

None of that depends on this week's oil price, which is why the pump matters less to an owner who can charge at home. For everyone else, the next fortnight is the test. If diesel is still close to 198p at the end of November, the 16% week will have stayed where it started, in the trading screens. Diesel has already set a record this autumn. The relief from this week has yet to arrive (our report on the record diesel price).

Sources

Business Recorder, "Brent oil price benchmark set for biggest weekly drop since 2020", 6 November 2026, brecorder.com
Department for Energy Security and Net Zero, "Weekly road fuel prices", updated 3 November 2026, gov.uk
Visordown, "Why are UK fuel prices still so high when oil prices are falling?", 6 November 2026, visordown.com
RAC, "Price of diesel reaches record high", 28 September 2026, media.rac.co.uk
RAC, "Petrol and diesel prices" (Fuel Watch), accessed 7 November 2026, rac.co.uk