Fuel · Updated every week · Figures to 24 Aug 2026
Why is Diesel quietly taxing everything you buy?
This week diesel costs $5.65 and regular costs $4.08 - a gap of $1.57 a gallon, against a long-run average of $0.26. That gap is a bill everyone pays, whether they drive a diesel or not.
Diesel and petrol used to cost about the same. For most of the past thirty years the gap between the two pumps was small change, and in plenty of weeks diesel was the cheaper fuel. That has changed, and it hasn't changed back: this week diesel costs $5.65 a gallon and regular costs $4.08. The chart shows the gap between them for every week since 1994 - one line, because the gap is the story.
So, what are we looking at, exactly?
Every point is a simple subtraction: the average price of diesel that week, minus the average price of regular. Above the zero line, diesel is dearer. In the early years the line regularly dipped below - diesel really was the cheap pump once. Around the mid-2000s it crossed for good, as cleaner diesel became more expensive to make just as more of the world wanted it. Then 2022 sent the gap somewhere it had never been, and it has never fully come back down.
The gap is now running at
6.0× its long-run average
In its early years this series averaged small change and dipped below zero in 322 separate weeks - diesel used to be the cheap pump. The current $1.57 gap is 6.0 times the long-run average.
Calculated from the chart aboveThe gap has been above a dollar in 14% of the last three years' weeks, and it's above a dollar now. It dips, but it doesn't stay down.
Calculated from the chart aboveWhy should anyone with a petrol car care?
Because almost everything in your house arrived on diesel. Trucks, trains, ships and tractors run on it, which makes this gap a hidden charge on moving goods around. When it stretches and stays stretched, the cost travels down the supply chain and shows up, months later, in your shopping. The truckers' pump is an early warning for everyone else's prices.
What this chart can't tell you
A national average hides a lot: California's diesel and California's regular have their own relationship, and so does every other region. The chart also can't say why the gap moved in any particular week - refinery problems, winter heating demand (heating oil comes from the same part of the barrel) and tax changes all tug at it. And the newest point is provisional until next Monday's release replaces it.
Further reading
All of our numbers come from live, free government data - here, the US Energy Information Administration's weekly pump survey, which prices both diesel and regular every Monday. The gap is our own subtraction, and this page updates when the new week lands.
If you want to dig deeper, EIA publishes both full price histories free - and the copy button under our chart takes the chart with its source attached.