Is dirty diesel a concern for caravanners?

Australia’s temporary move to allow higher sulphur diesel into the market may be helping keep supply steady, but for people towing caravans, running modern 4WDs or heading remote, it also highlights another important consideration.

Modern diesel engines are far less forgiving than the old ones, and dirty fuel, even slightly dirty fuel, can quietly cause problems long before you realise what is happening.

In simple terms, the Australian government is not importing “dirty fuel” in the way people often imagine. What it has done is temporarily allow the import and local supply of diesel with a higher sulphur content than normal to ease shortages and keep regional supply moving.

Under the temporary change, the allowable sulphur level has been lifted from the usual 10 parts per million to about 50 parts per million for a limited period, which means Australia can bring in additional fuel that would normally be sold into markets with lower standards.

If you grew up around older diesels, you will remember how tough they were. They would run on almost anything that vaguely resembled fuel and keep going with a shrug. Modern engines are a different story.

Today’s common rail diesels operate at extremely high pressures and rely heavily on emissions systems to stay clean and efficient. That makes them quieter, smoother and more economical than ever before, but it also makes them far more sensitive to fuel quality. When the fuel is not as clean as it should be, the effects are rarely dramatic at first. Instead, they creep in slowly and often show up in ways owners don't immediately connect to fuel.

You hear it around campgrounds and servo forecourts... talk about more frequent DPF regens, slightly higher fuel consumption, small drops in performance and warning lights that seem to appear and disappear without much explanation.

Owners of newer vehicles sometimes mention using more AdBlue than they expected. None of these things automatically mean something is wrong but taken together they often point to one simple factor: inconsistent fuel quality.

“A lot of the time people come in worried about the vehicle itself, but once you start asking questions about where they have fueled up and how they use it, the picture changes,” explained Queensland-based diesel specialist Tom Shanks from Master Tech Diagnostics and Repairs.

“More frequent regens, slightly higher fuel use and those small performance changes often trace back to fuel quality rather than a mechanical fault.”

He goes on to explain that when diesel contains higher sulphur levels or small amounts of contamination, it produces more soot during combustion. That soot builds faster in the diesel particulate filter and the vehicle has to regenerate more often to clean itself out.

More regens mean more fuel burned and more heat cycling through the system. Over time, that extra workload adds wear, particularly so for travellers towing heavy vans or pushing long distances in hot conditions.

Remote travel adds another layer. Around major towns and highways, fuel quality tends to be fairly consistent, but once you head inland across the Nullarbor, up through the Territory or into smaller regional areas, consistency can vary. Storage times change, turnover varies and environmental conditions are tougher. Most of the time everything is fine, but the margin for error is smaller than it used to be.

One of the easiest and most practical steps caravanners can take is improving filtration before the fuel reaches the engine. A quality secondary fuel filter helps capture fine particles and water, reduces strain on the factory system and lowers the risk of excessive injector wear.

Fuel additives also have a role if used sensibly.

“Products like Penrite Convoy DPF Cleaner can definitely help in certain situations, especially for vehicles that spend a lot of time towing, idling or doing shorter runs where the DPF does not always get a proper clean-out,” Shanks said.

“They're not a substitute for clean fuel or proper filtration, but they can support cleaner combustion and help manage soot levels when conditions are working against you."

"If fuel has been sitting for long periods or contamination is suspected, products like Würth’s biocide can also be useful, but again it is a targeted fix rather than something most travellers need to use routinely. The key is to use them occasionally and as directed, not as a fix for an underlying problem," he continued.

"Even with a cetane improver it will not significantly offset the extra emissions-system workload that comes with higher sulphur diesel.”

A few simple habits also help, like choosing busy fuel stops with good turnover and keeping your tank topped up in remote areas to reduce condensation. Also, being aware of any small changes in how the vehicle feels can often tell you more than a dashboard light.

Many caravanners will never experience a serious fuel-related issue, but when you're towing a 'van over long distances or travelling remote, some preventative measures can pay off in the long run.

Related: Fuel shortages, jerry cans and panic buying