How to remove fish oil from my 4wd chassis

How do I remove Fish Oil from my chassis?

March 27, 2024

If you've ever crawled underneath your 4WD and ended up covered in sticky black fish oil, you're certainly not alone.

For decades, fish oil has been one of the most common ways Australians have tried to protect their chassis from rust. It can be effective at slowing corrosion, but it also comes with one major downside—it stays sticky.

That sticky coating attracts sand, red dirt, dust and road grime, making the underbody difficult to clean and often leaving a mess every time you work underneath your vehicle.

Whether you're preparing to apply a different rust protection product, servicing your 4WD or simply tired of the build-up, here's what you need to know about removing fish oil properly.

Why Remove Fish Oil from Your Chassis?

There are plenty of reasons why people choose to remove an old fish oil coating.

Some of the most common include:

Switching to a newer style of rust protection.
Preparing for suspension or mechanical repairs.
Removing years of built-up dirt and grime.
Cleaning the vehicle after repeated beach trips.
Selling the vehicle.
Wanting a cleaner underbody that's easier to maintain.

While fish oil can provide corrosion protection, its sticky nature means it often becomes a magnet for sand, dust and red dirt.

Can You Simply Pressure Wash It Off?

Unfortunately, no.

A pressure washer is excellent for removing loose dirt and mud, but once fish oil has bonded to the chassis, water alone usually isn't enough.

You may remove some loose contamination, but the oily coating generally remains behind.

In most cases, you'll need a solvent or degreaser first, followed by a thorough wash.

The Best Ways to Remove Fish Oil

Every vehicle is different, and the age of the coating will influence how difficult it is to remove.

These are the methods that generally work best.

1. Mineral Turpentine or White Spirits

One of the most common methods is using mineral turpentine or white spirits.

These solvents help soften old fish oil so it can be wiped away or pressure washed off.

Pros

Readily available.
Effective on stubborn coatings.
Good for smaller sections.

Cons

Labour intensive.
Can require multiple applications.
Strong smell.
Wear gloves and work in a well-ventilated area.

2. Wax and Grease Remover

Wax and grease remover works well for cleaning residue once the heavier coating has been removed.

It's particularly useful if you're preparing the surface for another protective coating.

This method often requires several applications depending on how thick the fish oil has become.

3. Heavy-Duty Citrus or Oil Degreasers

Modern degreasers designed to break down grease and oil can be an effective alternative.

Apply the degreaser according to the manufacturer's instructions, allow it to dwell for the recommended time, then pressure wash thoroughly.

Some heavily contaminated vehicles may require more than one treatment.

4. Steam Cleaning

Commercial steam cleaning can also help soften and remove stubborn fish oil.

The combination of heat and pressure makes it particularly effective where years of dirt have become embedded in the coating.

While most people don't own a steam cleaner, many professional detailing businesses offer this service.

The Biggest Mistake People Make

One mistake we see regularly is trying to remove the entire coating in one afternoon.

If your 4WD has been treated with fish oil for years, it's often better to tackle the job in sections.

Working methodically produces a cleaner result and makes the job much more manageable.

In Our Experience

One of the most common comments we hear at 4WD shows is:

"I wish I'd never put fish oil on it."

Usually it's not because it failed to protect the chassis.

It's because everything sticks to it.

After beach trips, sand clings to the coating. After driving through red dirt, the underbody can stay stained for months.

That's one of the reasons we developed Beach Barrier.

Rather than creating a permanently sticky coating, it forms a protective layer that helps repel salt, sand and water while making the vehicle much easier to clean after your adventures.

What Should You Apply After Removing

Fish Oil?

Beach Barrier Underbody Protection Spray

Once you've removed the old coating, it's the perfect opportunity to protect your chassis again.

Leaving bare steel exposed isn't recommended, particularly if your vehicle regularly visits the beach.

Beach Barrier is designed to be applied before beach driving, helping repel salt, sand and water from the underbody while making post-trip cleaning much easier.

Unlike traditional fish oil, it doesn't leave a permanently sticky coating that continually attracts dirt.

Frequently Asked Questions

Does fish oil eventually dry?

Some fish oil products dry more than others, but many traditional fish oil and lanolin-based coatings remain tacky for a long time, particularly underneath vehicles where airflow is limited.

Can I pressure wash fish oil off?

Not usually.

A pressure washer alone is unlikely to remove established fish oil coatings. A solvent, degreaser or steam cleaning is normally required first.

Should I remove old fish oil before applying another rust protection?

If you're changing to a different type of protective coating, cleaning away the old product first generally gives the new coating the best chance to bond properly.

Always follow the application instructions for your chosen product.

Can I apply Beach Barrier over Fish Oil?

No. For the best performance, remove old fish oil and other heavy coatings before applying Beach Barrier. A clean surface allows it to bond properly and perform as intended.

Is fish oil better than lanolin?

Both have been used successfully for many years to help reduce corrosion.

The main difference for many owners is maintenance.

Traditional fish oil and lanolin products can remain sticky and collect dirt over time, whereas newer protective coatings are often designed to make ongoing cleaning easier.

How often should I re-protect my chassis?

That depends on how often you drive on the beach, through mud or in harsh environments.

For most people, you want to re-apply Beach Barrier before beach trip, if it has been over a month since your last trip. The 5 mins application time is worth it in the long run.

You can also see if Beach Barrier is still present, by wetting the chassis. The hydrophobic properties of Beach Barrier are easy to see when it's still working.

Final Thoughts

Removing fish oil from your 4WD chassis isn't the most enjoyable job, but it can make future maintenance much easier.

Whether you're switching to a different rust protection product, carrying out repairs or simply tired of the sticky build-up, taking the time to remove old fish oil properly gives you a clean starting point.

Once the chassis is clean, protecting it before your next adventure—and thoroughly cleaning it afterwards—will help keep your 4WD in excellent condition for years to come.

Continue Your 4WD Maintenance Journey

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