How does Refil know if petrol prices are about to rise?

Published on 2026-10-07

Refil doesn't guess: it combines what pump prices are doing today, the direction of crude oil and a statistical model that estimates the probability that petrol and diesel will rise by at least a penny a litre the following week. In the UK that model was tested against the government's own weekly price series, which it never saw while it was being built, and it only alerts you above a measured threshold.

Two signals that watch today

The first is crude oil. Brent takes one to two weeks to reach the pump, so when it moves 8% or more in four to seven days, that ramp tells you what is coming. For the UK Refil follows Brent in dollars rather than in euros, so a currency that isn't yours doesn't creep into the signal. A single odd reading that reverses the next day is thrown out.

The second watches our own price history: has the national average already started to move today? It takes two snapshots at fixed times, 10:00 and 18:00 UK time, and compares each with the same slot the day before.

The fixed times matter. The first version compared a mid-morning price with the previous day's close, and in markets where prices go up and down during the day it mistook that swing for a rise: alerts fired between 12:00 and 15:00 UTC were right only 42% of the time. The same rule on comparable prices was right 86% of the time over the same period, which is why it changed.

The weekly model: 21 years of prices and a probability

Getting ahead of a rise needs a different question: will the price go up by at least a penny a litre by next Monday? The model answers with a probability, not a yes or no. It learns how the pre-tax price follows the wholesale cost of petrol and diesel in New York Harbor and Brent crude, using the European Commission's Weekly Oil Bulletin going back to 2005.

It blends two approaches: a classic cost pass-through model that also lowers its own confidence when it has been wrong for a few weeks, and a machine-learning model trained on many countries at once. It runs on Tuesdays and Thursdays, and if fresh cost data hasn't arrived in time it publishes nothing rather than pretending nothing has moved.

It was chosen without looking at 2024 to 2026, which were held back for a single final exam. In that exam, when the model said 70% or more, prices across the European markets rose by at least one cent in 84% of 152 alerts, and its calibration error (a score where lower is better) fell from 0.183 to 0.158 compared with the previous model.

Why the UK is the cleanest test

The UK was the first market outside the EU bulletin. Refil checks it against DESNZ's weekly road fuel prices, the official series in pence per litre including duty and VAT, which runs back to 2003, with the wholesale cost converted into pounds.

No British data was used to design or tune the model, so its UK record is a genuinely clean test. From 2018 to 2026, when it said 70% or more it raised 25 alerts and 24 of them were followed by a rise of at least a penny. None was followed by a fall of a penny or more.

The flip side is that alerts are rare. Only around one week in seven sees a rise of a penny or more in the UK, and the model only speaks when the DESNZ week lines up with the EU bulletin week. Few alerts, but ones worth acting on.

What it doesn't promise

It is a probability. It won't tell you the exact number of pence, and 70% means that three times in ten the rise won't come. In a crisis the link between cost and pump price breaks: across the European markets, the first version's “safe” alerts in 2022 were right only 57% of the time.

So in the UK a push alert only goes out at 70% or more and with wholesale costs rising, never more than one every 72 hours, and not if you already had a same-day rise alert in the previous 72 hours. If its live record drops below 60% after at least ten scored alerts, it switches itself off.

Every alert is scored afterwards against what the national average actually did, and it only counts as a hit if the price moved in the direction we called. The prices themselves come from the UK's statutory open fuel price data.

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