If you drive a modern diesel 4X4, particularly one with a DPF, then this article’s for you. Honestly, anyone heading out into Australia’s arid interior should be paying attention to the risk of a fire in long grass. The only ones who can probably switch off right now are those behind the wheel of a Unimog.
What’s the Risk?
Fire. We’re not being dramatic here, we’re talking about the kind of blaze that can gut your vehicle and leave you stranded, hours from help. It all comes down to dry grass, and high heat, it’s a combination that’s never going to end well.
Whether you’re heading along the Canning, out to the Madigan Line, or into the lesser-known corners of the Gibson and Great Victoria deserts, one thing’s for sure, spinifex doesn’t care how much you spent on your rig.
The Spinifex Trap
Spinifex is tough, wiry desert grass. It’s full of oily resin, which means once it gets hot enough, it burns like a firelighter. And it’s everywhere.
This stuff loves to wedge itself up into your chassis rails, under crossmembers, around your transmission, and especially near your exhaust. If it builds up unnoticed, and your exhaust is hot enough (spoiler: it usually is), you’re in strife.
DPFs only make things worse (we’ll come back to that in a tick).
And it’s not just about fire. Tall grasses and seed heads can get drawn into your radiator and intercooler fins, causing overheating dramas long before you realise what’s happening. Out here, losing cooling performance can be catastrophic.
Preventing a Burnout (Literally)
Here’s what we recommend if you’re heading out bush:
- Do Regular Underbody Checks
Every time you stop for a break, even just a quick cuppa, take five to crawl underneath and check for built-up grass. It’s a pain, but so is watching your pride and joy go up in smoke.
- Add Underbody Guards with Fire Prevention in Mind
Steel or alloy bash plates are great, but consider adding mesh guards or deflectors in areas where grass tends to collect, like behind the transfer case or around the DPF. Some 4X4ers even mount sacrificial mesh underneath the vehicle to catch the spinifex before it reaches the hot bits.
- Shadecloth for the Win
A $20 bit of shadecloth zip-tied across your grille could be the best mod you make before your next trip. It keeps seeds out of your radiator and intercooler without blocking airflow. It’s a bush mechanic classic that actually works. Make sure you clean between your radiator cores as well, a long zip tie or air gun can help dig out the debris.
The DPF Danger
Here’s where things get real.
Modern diesels fitted with a DPF (Diesel Particulate Filter) are at a much higher risk in these conditions. A DPF traps soot and particulate matter from the exhaust, then burns it off in a process called regeneration. To do this, it increases exhaust gas temps, sometimes upwards of 600°C.
You read that right.
If you’ve got spinifex tucked in next to your DPF during a regen cycle, you could literally ignite it. There have been cases of 4X4s catching fire this way, especially in newer vehicles that don’t give much warning when a regen is kicking off.
Some vehicles will force a regen while you’re driving. Others can do it at idle without telling you. Either way, it’s risky if you’re not on top of it.
What You Can Do:
- Know your vehicle: Learn how and when your DPF regenerates. Check your owner’s manual, forums, or better yet, ask your local mechanic.
- Avoid idle regens in grassy areas: If you stop in tall grass, switch the car off. Don’t risk a regen kicking off while you’re having lunch.
- Install a DPF monitor: Some aftermarket setups let you track regen cycles and exhaust temps. If you’re touring remotely, this is cheap insurance.
Final Word
Grass fires under vehicles are more common than most people realise, and the consequences are serious. But the good news is, prevention is simple if you stay switched on.
Whether you’re running an older turbo-diesel or a brand new 4X4 with every modern sensor under the sun, a few bits of shadecloth, some regular checks, and a bit of knowledge could save your rig, and your trip.
Got a tip for stopping grass fires before they start? Flick us a message or tag us in your rig photos on socials, we’d love to see how you’re prepping your 4X4 for the outback.
