Higher petrol and diesel prices were the single biggest reason Inflation rose to 3.1% in August, pushing transport costs up and reminding drivers how quickly forecourt prices feed through.

Rising fuel prices were the main reason UK inflation climbed in August, according to figures from the Office for National Statistics (ONS) published on 16 September. Motor fuels made the largest single upward contribution to the increase in the Consumer Prices index (CPI), which rose to 3.1% over the 12 months to August from 2.9% in July.

For anyone who drives, the shift was visible at the forecourt. Petrol prices rose by around 9.1 pence per litre between July and August, while diesel climbed by about 14.2 pence per litre. Those monthly jumps were large enough to move the entire national inflation figure, illustrating how sensitive the headline rate can be to what happens at the pumps.

How transport pushed the rate up

Fuel sits within the transport category of the inflation basket, and that category was the chief driver of August's increase. Transport's annual inflation rate rose to 4.6% in August from 3.6% in July, more than a full percentage point higher in a single month. Because transport is a substantial part of household spending, a sharp move there carries disproportionate weight in the overall figure.

The mechanics are straightforward. The CPI is a weighted average of price changes across the goods and services households buy. When a heavily weighted and volatile component such as motor fuel swings upward, it can lift the headline rate even if most other prices are broadly stable — which is largely what happened in August, when core and services inflation held steady.

A change in the contribution, not just the level

It is worth being precise about what fuel did. The point is not simply that fuel is expensive, but that its contribution to inflation increased between July and August. Prices that are rising at a steady rate contribute steadily to inflation; it is an acceleration in those prices that pushes the annual rate up. In August, fuel prices accelerated, and so their contribution to the change in inflation grew.

This is why coverage focused on transport as the driver of the move from 2.9% to 3.1%. Other categories contributed in their own directions — food, for instance, was a steadying influence, unchanged at 1.3% annual growth — but transport and fuel were the decisive force behind the upward shift of 0.2 percentage points in the headline rate.

Pressure building in the pipeline

Separate ONS data on producer prices, also published on 16 September, point to cost pressures further up the Supply chain. Input prices paid by manufacturers were 6.1% higher than a year earlier in August, and Crude Oil input prices were up 26.7% over the year. Prices for coke and refined petroleum products provided one of the largest upward contributions to factory-gate output price inflation, with those prices rising 8.6%.

Producer prices measure costs at the factory rather than in the shops, but they can foreshadow movements in consumer prices, because higher costs for oil-derived products eventually filter through to the fuel and goods households buy. The ONS notes that recent oil and energy data have been affected by conflict in the Middle East, a reminder that forecourt prices in Britain are shaped substantially by global forces.

Why fuel matters so much

Fuel occupies an outsized place in how inflation is felt. It is a frequent, visible purchase, its price is displayed in large numbers on every forecourt, and for many people it is a non-negotiable cost of getting to work or running a household. Increases are noticed quickly and widely, which gives fuel a psychological weight beyond its statistical share of the basket.

It is also among the most volatile components of inflation, capable of swinging sharply in either direction from month to month. That Volatility cuts both ways: just as rising fuel prices pushed inflation up in August, a subsequent fall could pull it back down. The current data capture the August increase but say nothing certain about what comes next.

The bigger inflation picture

Stepping back, the August figures show inflation being nudged higher by a specific, volatile Factor rather than by a broad-based surge across the economy. Core inflation, which excludes energy, food, alcohol and tobacco, held at 2.6% on the CPI measure, and services inflation was steady at 3.4%. That combination suggests the underlying trend was relatively stable and that fuel did much of the work in lifting the headline.

For households, the immediate consequence is higher costs at the pump and a slightly larger squeeze on budgets already contending with rising rents and energy bills. For anyone trying to read the economy, the lesson is about attribution: the rise to 3.1% was, on the ONS's own account, led by fuel and transport. Whether that pressure persists depends on oil and pump prices in the months ahead — a question the current figures raise but cannot answer.

From barrel to forecourt

The journey from a global oil price to the number on a forecourt sign involves several steps, which helps explain why fuel can move inflation so sharply. Crude oil is refined into petrol and diesel, distributed, and sold with fuel duty and VAT added on top. Movements in the underlying oil price, and in refining and wholesale costs, feed through to pump prices with a short lag, so a jump in global oil markets can translate into higher forecourt prices within weeks.

That transmission is visible in the producer price data, where crude oil input prices were 26.7% higher over the year and refined petroleum products made a large contribution to factory-gate inflation. Those Upstream costs are part of the chain that ends with the petrol and diesel prices households pay, even though the two sets of figures are measured at different points. Because so much of the pressure originates in global oil markets, it is largely outside domestic control. Events far from the UK — shifts in supply, changes in demand, or geopolitical tension such as the conflict in the Middle East that the ONS cites — can move the price of a barrel and, in turn, the cost of a tank of fuel. That external dependence is part of why fuel is such an unpredictable component of inflation. That volatility can reverse in a single month.