Sorting Out Your Undercarriage Before the Rust Sets In

Don't bother crawling around on your hands and knees with a standard hose nozzle; you'll just end up soaked and frustrated. I reckon the best 50 bucks you'll ever spend is on an underbody pressure washer attachment with the little wheels. If you're on a budget, just chuck a rectangular garden sprinkler under the car and let it run for 15 minutes, moving it every now and then. I learned this the hard way after a trip to K'gari (Fraser Island), I thought a quick hose-down was enough, but six months later I found salt crystals still hiding inside the frame rails. Never again.

Fresh water is good, but if you've been driving through salt spray on the coast, it won't always shift the bonded salt. I'm a big fan of products like Salt-Away or the Bowden's Own Muck Off. You just click them into your hose or foam gun. It actually breaks the bond of the salt so it slides off rather than just getting wet. Truth be told, I use this on my missus' SUV too, even though she never leaves the bitumen, that sea breeze in the arvo carries more salt than you'd think.

If you've just come back from the Nullarbor or the Red Centre, do not, I repeat, do not, let that dust get wet and then dry again. It turns into concrete. My go-to method is a dry blow-out first with an air compressor or a leaf blower if you've got one. Get as much loose stuff out while it's dry. Then, hit it with a heavy-duty degreaser or a dedicated 4x4 wash. I've seen blokes spend three days trying to pressure wash red mud out of a chassis because they didn't bother to blow the loose dust out first.

Once it's clean and dry, you want some sort of barrier. Some people swear by fish oil, but honestly, the smell is enough to make you want to sell the car. I prefer a lanolin-based spray like Lanotec or even a dedicated underbody wax. It stays slightly tacky, which some people hate because dust sticks to it, but I reckon it's better to have a bit of dusty lanolin than a rusted-out floor pan. Just stay away from the cheap 'black paint' cans that cover up rust, they usually just trap the moisture underneath and make it worse.