The Diesel Problem: Why Petrol Easing Doesn't Mean the Crisis Is Over

If you've filled up a regular car this week, you might have walked away thinking the worst is behind us. Petrol has slipped back to roughly $1.93 a litre across the big cities. The headlines have gone quieter. Service stations that ran dry in March are mostly back in business.

Here's what's really going on, though. The half of the fuel crisis that actually decides what you pay for groceries hasn't eased at all. It's diesel. And diesel is still sitting between $2.75 and $3.00 a litre in plenty of places.

The fuel you don't buy is the one that matters most

Most households think of the fuel crisis as a petrol story, because petrol is the bowser they personally use. But the numbers tell a different tale. Australia burns through about 92 million litres of diesel every single day, more than double the roughly 44 million litres of petrol. Diesel runs an estimated 70 percent of the nation's freight task. It powers the trucks, the trains, the harvesters, the mining gear and the generators that keep regional towns ticking over.

So when diesel gets expensive or scarce, it doesn't just hit truckies. It works its way into the price of everything that arrives on a truck, which is to say almost everything. The National Farmers' Federation has warned that sustained diesel disruption could push some food prices up by as much as 50 percent. That's not a figure plucked from thin air. Winter wheat planting season is upon us, and sowing a crop needs two things in short supply right now: diesel for the machinery and fertiliser, much of which is itself derived from fossil fuels.

The thing is, a litre of diesel and a litre of petrol look identical to a motorist. But to the economy they're nothing alike. Petrol is largely discretionary. Diesel is the circulatory system.

How thin is the margin, really?

Let's put this in perspective. As reserves stand in mid-May, Australia is holding somewhere around 30 to 34 days of diesel, depending on which week's figures you read and whether you count fuel still on ships heading our way. Petrol sits a touch healthier at around 44 to 46 days.

Thirty-odd days sounds like a buffer until you remember the benchmark. The International Energy Agency asks member countries to hold 90 days of net imports. Australia is the only IEA member that doesn't, and we've been falling short of that obligation since 2012. Back in 2002, before the refinery closures really got going, the country sat on something like 310 days of cover. We have quietly let that buffer erode for two decades.

The reason diesel is the sharper worry comes down to where it's made. Australia now imports more than 90 percent of its refined fuel, and the two refineries we still run, Ampol's Lytton plant in Brisbane and Viva Energy's facility in Geelong, together cover only around 10 to 20 percent of national demand. Both of those refineries skew their output toward petrol and jet fuel. A surprisingly large share of our diesel comes in by tanker from South Korea, Singapore, Malaysia and Taiwan, and those tankers have to thread a needle that's currently very tight.

Why the Strait of Hormuz is on your shopping receipt

The trigger for all this is the conflict in the Middle East and the disruption around the Strait of Hormuz, the narrow shipping channel that a huge slice of the world's refined diesel passes through. When that channel gets risky, freight rates spike, insurance costs jump and cargoes get rerouted or delayed.

Industry contacts tell me the diesel market is far less forgiving than petrol in moments like this. There's simply less spare diesel sloshing around Asia's spot market, because diesel demand globally is strong and inventories were already lean before the conflict flared. Petrol, by contrast, has been comfortably supplied. That's the real story behind the split you're seeing at the bowser: same crisis, two very different outcomes for the two fuels.

The government's response has leaned heavily on diesel for exactly this reason. Four additional diesel cargoes, around 200 million litres all up, are expected to dock in late May or early June. Canberra has already released 762 million litres from emergency reserves and temporarily relaxed fuel quality standards to let an extra 100 million litres flow in each month. To be fair, that monthly top up is useful, but it's worth keeping in mind it amounts to barely a single day of national consumption.

What it actually means at the bowser

For anyone driving a diesel ute, a 4WD or a van for work, the practical upshot is that you shouldn't expect diesel to track petrol back down in a hurry. The two have decoupled, and they're likely to stay that way until shipping settles. The 32 cent excise cut running from 1 April to 30 June does apply to diesel as well as petrol, so the headline figure you see already has that relief baked in. When the cut expires at the end of June, diesel drivers will feel the snap back just as petrol drivers will.

A few things make a genuine difference right now. First, the spread between the cheapest and dearest diesel in a single suburb has blown out during the crisis, far wider than the usual gap. That means shopping around pays more than it normally does. It's worth checking diesel prices near you rather than assuming your regular servo is competitive, because the old loyalties haven't held up well under supply stress.

Second, if you run a vehicle that can take either fuel, the maths has shifted. With unleaded petrol prices sitting well below diesel, the long standing assumption that diesel is the cheaper fuel to run simply doesn't hold this month.

Third, regional drivers are wearing the worst of it. The crisis has hit New South Wales and Victoria hardest for outages, while parts of Western Australia continue to carry the country's steepest diesel pricing. If you're planning a long regional run, fill up before you leave the metro area and check the price trends for your route rather than gambling on a remote servo having both stock and a fair price.

The bigger picture

What most people don't realise is that this crisis has quietly forced a structural change. Canberra's $14.8 billion fuel resilience package includes a first of its kind, government owned reserve holding around a billion litres, and notably it focuses on diesel and aviation fuel rather than petrol. Combined with tougher minimum stockholding rules on the private sector, the plan aims for at least 50 days of onshore cover. That still falls short of the IEA's 90 days, but it's the first serious move in the right direction in a generation.

Going back a few decades, Australia refined its own fuel and barely thought about supply security. Eight refineries became two. The cost of that drift was invisible right up until a shipping lane on the other side of the world started deciding the price of a loaf of bread in Bendigo. Diesel is where that vulnerability shows up first, and it's where the recovery will be slowest.

The takeaways:

The fuel industry rarely makes headlines until prices spike, and even then the attention tends to land on petrol. Diesel is the one to watch through winter. Keep an eye on this space.