Suspension Oil, the Stuff We Never Talk About.

There’s a moment every rider knows that soft, silent float when your fork breathes in the terrain and turns chaos into control. It’s magic.

It’s also something most of us never think twice about, at least not until our suspension feels sticky or a seal starts weeping.

And yet, inside every fork and shock on every bike we ride is a cocktail of oils and fluids that make all that smoothness possible. The dirty little secret? Those fluids aren’t exactly friendly to the world we ride in.

It’s strange, really. Mountain biking is built on a love of nature trees, dirt, air, freedom yet so much of our gear depends on petroleum-based products with environmental footprints that nobody really talks about. So I wanted to dig into the reality of suspension fluids, where they come from, where they end up, and what the future might look like if we took sustainability seriously.

The Hidden Cost of Smoothness

Suspension fluid doesn’t get the same attention as brake fluid, tire compounds, or carbon manufacturing. It’s quiet, tucked away, and easy to ignore. But between fork bath oil, damper oil, shock fluid, and lubricants, we actually use a lot of the stuff.

A typical fork holds around 80–120 ml of fluid. A shock adds another 10-40 ml. Most riders who stay on top of maintenance get both serviced each year. Now multiply that across tens of millions of mountain bikes worldwide.

Very conservatively, the MTB community is burning through around 5 million litres of suspension fluid every year. That’s a number you feel once you hear it. And the problem isn’t just the sheer volume it's the fact that most of these fluids are petroleum-derived, slow to break down, and toxic to aquatic life.

A single litre of used oil can pollute a million litres of fresh water if it’s dumped improperly.

Where All That Fluid Goes

Suspension, by design, is not perfectly sealed. Dust wipers wear. Stanchions get micro-scratches. Temperature changes expand and contract oil films. The reality is that a little fluid escapes during almost every ride just a few micrograms at a time, but enough to matter at scale.

Then there’s the maintenance waste: fork drains, oil bleeds, cleaning fluids, grease. Most shops dispose of them responsibly, but plenty of home mechanics may not.

As someone who's spent so much time cycling, fishing and surfing that realization hit hard.

What’s Actually Inside This Stuff?

Most suspension oil today falls into a few big categories:

• Mineral oils (the most common; petroleum-derived)

• Synthetic blends (better performance, same underlying source)

• Silicone-based fluids (stable, but energy-intensive and non-biodegradable)

• Bio-based oils (promising, but still niche)

Bio-based fluids are where things get exciting. Made from plant-derived esters, they’re far more biodegradable and less toxic.

The hitch? They can struggle with long-term viscosity stability, especially with the heat that modern forks generate.

Performance riders push fluids hard, and suspension companies are understandably cautious about warranty issues. So even though biodegradable oils exist, the industry hasn’t made a big jump yet.

Are Eco-Friendly Fluids Actually Viable Yet?

Short answer?

Sort of. It depends.

Environmentally friendly suspension oils are out there some fully plant-based, others blends and many of them are genuinely impressive. Riders who aren’t pushing bike-park laps every weekend might never feel the difference.

But it’s not yet a simple “swap it and forget it” situation:

• Some eco oils thin out when things get hot.

• Some swell seal materials not designed for them.

• Some aren’t yet approved by big manufacturers.

It’s a bit like the early days of tubeless sealant: the ideas are solid, the execution is improving every year, and sooner or later the whole industry will shift.

We’re just not quite there for universal compatibility.

A Thought We Don’t Entertain Enough: Using Less Fluid Overall

There’s another angle that gets overlooked: Maybe the problem isn’t just the fluid—maybe it's how much we rely on it.Modern suspension has grown bigger, faster, more complex. Lower legs are huge. Dampers are intricate. Everything uses more fluid than it did 10 or 15 years ago.But coil suspension the old-school kind doesn’t require nearly as much lubrication or damping fluid. Modern coil forks and shocks are lighter, more tuneable, and more refined than ever. They don’t eliminate oils, but they reduce the total amount used across a bike’s life.

Less complexity = fewer services = less waste.

There’s something elegantly sustainable about that.

So What Can We Actually Do?

You don’t have to quit suspension or go back to rigid bikes to reduce your impact. A few small habits go a long way:

• Let a shop handle your waste oil if you’re not sure where it goes.

• Keep your seals clean—they’ll leak less and last longer.

• Don’t over service. More oil changes aren’t always better.

• Choose eco-friendly cleaners and greases, even if your suspension fluid isn’t biodegradable yet.

• Support brands trying new things—it encourages more innovation.

Sustainability happens in steps, not revolutions.

Where We’re Headed

The good news is that suspension companies know this is an issue. The industry is already experimenting with:

• biodegradable ester-based oils

• safer additive packages

• longer-lasting seal materials

• friction coatings that need less lubrication

• recyclable damper cartridges

• lower-waste manufacturing processes

Suspension will always need some kind of fluid. But the type of fluid—and the environmental cost tied to it—is something we can absolutely redesign.

It’s encouraging to think that the next generation of suspension tech might not just be smoother or more adjustable, but genuinely cleaner for the trails we’re trying to enjoy.

Mountain biking has always had a strong environmental conscience. It feels like it's time our suspension caught up with our values.

If your looking for an alternative to you current set of bike oils and lubricants' a good place to start is with WPL or Stan's.

WPL make a range of biodegradable non-toxic bike products that will work as a good starting place for anyone wanting to move away from petroleum based production.

Key to this article is their WPL Shock-Boost Bio-Degradable suspension oil.

Stan's have also developed a range of bio-degradable lubricants that can be used to clean and lubricate your mountain bike.

The most important product for suspension though is their bio-degradable suspension oil in a range of weights from 2.5 to 20.

Its products like these that we need to support to enabled us to move forward in a clean environmentally conscious way