Rockets and Feathers: Why UK Petrol Prices Rise Faster Than They Fall
Published April 2026 · MPG Calc analysis
If you've ever noticed that petrol prices seem to shoot up overnight when oil rises but drift down for weeks when it falls, you're not imagining it. The phenomenon even has a name: rockets and feathers. Pump prices rise like a rocket and fall like a feather.
We tested whether this asymmetry is real in UK data. It is — and the gap between rising and falling is larger than most people realise.
Chart 1: Relative price movements, Feb–May 2026, indexed to 100. Crude oil is far more volatile than pump prices — but drivers rarely see prices fall when crude drops. The asymmetry chart below shows why.
Chart 2: The asymmetry in action. Each point is one 4-week window from 2018–2026 (430 observations). X axis: crude oil change (p/litre). Y axis: concurrent E10 pump price change (p/litre). Red = crude was rising (pass-through β = 0.49), blue = crude was falling (β = 0.06). The regression lines show the steepness of each. If pass-through were symmetric, the lines would be mirror images — they aren't; the rising slope is 7.5× steeper.
What the data shows
We analysed 427 weeks of pump prices from the Department for Energy Security and Net Zero alongside Brent crude prices from 2018 to 2026. Sustained crude oil movements do feed through to the pump: a three-month change in Brent crude explains about 37% of the variation in pump prices over the same window.
But the relationship is not symmetric.
When crude rises, pump prices respond at roughly 49p per £1 change in underlying crude cost within four weeks. When crude falls, pump prices respond at roughly 5p per £1 — about one tenth the speed.
In plain terms: forecourts pass on crude oil increases quickly and reliably. They pass on decreases barely at all.
The numbers behind a typical crude move
Take a 5% swing in Brent crude — roughly the kind of move that happens several times a year. At current prices, that's worth about 4 pence per litre in underlying crude cost.
Using the asymmetric pass-through rates from our analysis:
- A rising crude move of that size would typically add ~2.0p/litre at the pump within four weeks
- A falling crude move of the same size would typically save ~0.2p/litre — a tenth as much, if it arrives at all
On a 50-litre fill, a rising crude move costs you roughly £1. The equivalent fall in crude saves you around 10p. The gap — about 90p per fill — flows directly to retailer margin every time crude drops.
It's getting worse
The overall relationship between crude and pump prices is also weakening over time. The pass-through rate for rising crude was approximately 0.66 in 2018 — already asymmetric — and has declined significantly since, with recent years showing the least reliable relationship in the data.
This could reflect several things: UK refining margins and distribution costs becoming a larger fraction of the pump price, retailers maintaining wider margins during a period of energy-cost uncertainty, or the continued growth of supermarket fuel retailing, which sets prices competitively against other supermarkets rather than directly against crude.
Whatever the cause, the implication for drivers is that crude oil falls are passing through less of their value to the forecourt than they did five years ago.
What this means in practice
The Brent crude price is public information, updated in real time. A sustained fall in crude — say, more than 1.5% over 30 days — historically predicts a downward move at the pump within two to four weeks. But "historically predicts" is not the same as "guarantees", and the recent weakening of the relationship means the signal is less reliable than it was.
MPG Calc tracks this signal and shows it on the statistics page as part of the price signal model for individual stations. When crude is moving significantly in either direction, we show an implied pump price range — how much prices might move based on historical pass-through rates.
The policy context
Rockets and feathers is not unique to the UK, but the Competition and Markets Authority has specifically flagged it as a concern. The CMA's Supply of Road Fuel in the United Kingdom market study, published in July 2023, found evidence of asymmetric price adjustment — particularly for diesel from 2022 onwards — and recommended greater price transparency through a mandatory real-time reporting scheme. That scheme is the source of the data on this site.
Greater transparency doesn't automatically fix rockets and feathers: a forecourt that knows its competitors' prices in real time can price to maximise margin rather than compete it away. But it does give consumers the information to choose the cheapest local option, which is what MPG Calc is for.
How we measured this
The data. We used 427 weekly observations from the Department for Energy Security and Net Zero's Petrol and Oil Bulletin — the official government pump price survey, running from 2018 to 2026. Crude oil prices came from Brent front-month futures (BZ=F), converted to pence per litre at the prevailing GBP/USD rate each week.
The method. We fitted a regression line between crude price changes and pump price changes over a rolling window, then split the observations into two groups — weeks where crude was rising and weeks where it was falling — and fitted separate lines to each. The slope of each line is the pass-through rate, or β: how many pence the pump price moves for each penny change in the crude cost.
The lookback window matters. Short-term weekly crude moves show almost no correlation with pump prices — the signal is in sustained trends, not daily noise. A three-month (13-week) change in Brent crude explains about 37% of pump price variation over the same period (r² = 0.37). Shorter windows explain far less.
What the numbers mean. A pass-through rate of β = 0.49 means that for every 1p rise in the underlying crude cost per litre, pump prices have historically risen by around 0.49p within four weeks. A rate of β = 0.05 means the same 1p fall in crude cost reduces pump prices by only about 0.05p — roughly one tenth as much. On a typical 4p/litre crude swing, that's approximately 2.0p added at the pump when crude rises, versus around 0.2p saved when it falls.
The weakening trend. We estimated the rising-crude pass-through rate separately for each year. It was approximately 0.66 in 2018 and has declined significantly since — with the relationship between crude and pump prices becoming less reliable overall in recent years. The asymmetry between rising and falling crude has persisted throughout.
Source data: BEIS Petrol and Oil Bulletin (DESNZ). Crude: Brent front-month futures via Yahoo Finance. Full site methodology: How MPG Calc Works.