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Keep Your Undercarriage From Rotting Out

Your car's interior cops more abuse than you realise—UV damage, spills, body oils, and the occasional fast food disaster. Here's how to fight back.

Don't let Aussie salt and red dust eat your chassis from the inside out. This checklist covers exactly what you need to protect your rig's belly during the harsh summer heat.

SC
Sarah Chen Interior & Leather Specialist
| Updated: 27 February 2026
Keep Your Undercarriage From Rotting Out

Aussie Conditions

Australian UV is 15% stronger than Europe. Your dash and leather need proper UV protection, not just cleaning, especially if you park outside.
Quick Summary

Look, if you're hitting the beach this summer or trekking through the red dirt, your undercarriage is copping an absolute beating. I've seen brand new 300 Series Cruisers come into the shop with surface rust starting after just one Fraser trip because the owner didn't rinse the salt properly. This guide is a quick, no-nonsense checklist to get your underbody protected and keep it that way. Use it before you head off or right after you get back.

01

The Gear You'll Need

What You'll Need

0/8
Pressure washer with an underbody attachment — Don't bother crawling on your belly; a $30 rolling attachment from Bunnings is a lifesaver.
Lanolin-based spray (Fluid Film or Lanotec) — I reckon Lanotec is the gold standard for Aussie conditions. It doesn't dry out in 40 degree heat.
Degreaser (heavy duty) — Something like Bowden's Own Orange Agent works a treat on old grease and grime.
Long-handle stiff brush — For scrubbing those stubborn bits of mud stuck in the chassis rails.
Safety glasses — Trust me, getting a face full of salty mud and degreaser ruins your weekend real quick.
Chassis rail flushing tool — Basically a hose with a 360-degree nozzle to get inside the rails.
Microfibre rags — Old ones you're happy to chuck away afterwards.
Work light or headlamp — It's dark under there, even in the middle of a summer arvo.
02

Pre-Start Checklist

What You'll Need

0/4
Engine is stone cold — Never spray cold water or chemicals on a hot exhaust or diff. I've seen cracked housings from this.
Parked on a slight incline — Helps the water drain out of the chassis rails instead of pooling in the middle.
Check for grease leaks — Look at your CV boots and diff seals now before everything gets wet and messy.
Drain holes are clear — Poke a screwdriver into the chassis drain holes. They're usually blocked with red dust or sand.
03

The Protection Process

Tap each step to mark complete
01

The Initial Blast

Use the pressure washer to knock off the heavy stuff. Start from the middle and work your way out to the wheel arches.

02

Degrease and Scrub

Spray your degreaser on the greasy bits (diffs, transfer case). Give it 5 minutes to dwell, but don't let it dry in the sun.

03

Flush the Chassis Rails

Insert your flushing tool into the rail holes. Keep running water until it comes out clear. This is where most rust starts.

04

Final Rinse and Dry

Give everything one last rinse. If you've got a leaf blower, use it to blow out the standing water from the nooks and crannies.

05

Apply Protection

Once dry, mist your Lanotec or Fluid Film over everything metal. Avoid the brake rotors and exhaust pipe like the plague.

04

Final Inspection

What You'll Need

0/3
Brake rotors are clean — Check again. If you got overspray on them, use brake cleaner to wipe them down immediately.
No 'clumps' of wet sand — If you find a wet clump, it'll hold salt against the metal. Dig it out.
Transfer case and diff breathers — Make sure you haven't knocked any hoses loose while you were scrubbing.

Watch Out

Don't use 'rubberised' undercoat sprays on an older car. I made this mistake on a mate's Patrol once, it just traps moisture underneath the rubber and rots the metal twice as fast. Stick to oil or lanolin-based stuff so the metal can breathe. Also, keep the spray away from your exhaust; it smells like a wet sheep once it heats up if you're using Lanolin!

The Pro's Secret

If you've been in heavy salt, chuck a handful of salt-neutraliser (like Salt-Away) into your foam cannon. It breaks the molecular bond of the salt much better than plain water ever will.

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