What’s in WD-40? Breaking Down the Ingredients

WD-40 Ingredients Revealed: What’s Actually Inside the Iconic Spray

The WD-40 “blue can” (original formula) is a proprietary blend, but its main ingredients are well-known through public Safety Data Sheets (SDSs), regulatory filings, and independent analysis. As someone who’s worked with lubricants, solvents, and rust penetrants for years, I get asked this question all the time: “What’s in WD-40?” Whether I’m in a workshop, a garage, or teaching a class, WD-40 always comes up in the conversation. It’s one of those products that’s so widely used that people assume it’s some kind of miracle fluid. But few actually understand what’s inside the iconic blue and yellow can.

WD-40 Isn’t Just One Ingredient—It’s a Carefully Balanced Blend

First things first—WD-40 isn’t a single chemical. It’s a proprietary blend of several ingredients designed to do a few specific things: displace water, clean surfaces, dissolve light rust and grime, and leave behind a thin lubricating film. The company doesn’t officially disclose the exact formula, but through public Safety Data Sheets (SDSs), we can determine the key ingredients.

Here’s the real story behind what’s in WD-40:

• Aliphatic Hydrocarbons (e.g., decane, nonane, isoparaffins) ~45–50%—  Solvent base that helps dissolve grime, oils, and rust-scale; penetrates tight spaces.
• Petroleum Base Oils (e.g., mineral oil, light lubricating oil) ~15–25%—  Provides light lubrication and leaves a protective film after evaporation.
• Hydrotreated Heavy Naphtha (Petroleum) ~25–35%— Acts as both a solvent and a mild cleaning agent; contributes to water displacement.
• Carbon Dioxide (CO₂) <5%— Used as the propellant in the aerosol can (non-flammable alternative to hydrocarbons).
• Fragrance and Dye Trace amounts— Added for scent and distinctive appearance (light amber color).

NOTE: These ranges are approximate and can vary slightly by region due to local regulations. For example, European and U.S. SDSs show similar but not identical chemical identifiers.

What WD-40 does well and what it doesn’t do well

Let me be clear—WD-40 is not a high-performance lubricant, and it’s NOT a VERY GOOD RUST PENETRANT, even though it’s advertised as one. It doesn’t have the viscosity or load-carrying capacity of true industrial lubricants. While WD-40 is excellent at water displacement and offers some lubrication, it doesn’t contain acidic or chelating agents that attack rust. But that’s not what it was designed for. The original intent of WD-40 (which stands for Water Displacement, 40th formula) was to prevent corrosion on missile components. Over time, its uses exploded across industries and homes worldwide.

This article explains the difference between a light lubricant like WD-40 and a real rust penetrant like PB Blaster.

Why it works

The solvents in WD-40 are thin enough to wick into tight crevices, like between a rusted bolt and nut, and displace moisture. That’s crucial when dealing with corrosion. Once the solvents evaporate, the light oil residue helps prevent more moisture from getting in. It’s also effective at cleaning grime and removing adhesives, making WD-40 a true multi-tasker.

So, WD-40 is mostly solvent, with just enough light oil to leave a protective film behind.

The Role of Each Ingredient in WD-40

1. Aliphatic Hydrocarbons— These make up nearly half the volume of WD-40. They’re light, low-viscosity solvents that dissolve oils, greases, and mild corrosion. They also evaporate quickly, which is part of why WD-40 doesn’t hang around long on surfaces.

2. Petroleum Base Oils— These are the real lubricating agents in WD-40, but they’re very light—think of them more like 3-in-1 oil than motor oil. They’re good for freeing up a sticky hinge or preventing flash rust, but they’re not meant for high-load or high-speed applications.

3. Hydrotreated Heavy Naphtha— This is a refined solvent that’s less toxic than untreated naphtha. It helps dissolve residues and displace water. If you spray WD-40 on a wet bolt, it’s this ingredient that helps push the water out.

4. Carbon Dioxide Propellant— WD-40 used to use flammable hydrocarbon propellants, but today it uses CO₂. It’s safer and non-flammable, making the spray easier to use in enclosed spaces or around ignition sources.

What WD-40 Doesn’t Contain

There are a lot of myths floating around about what’s in WD-40. Let’s clear a few of them up:

• WD-40 does not contain silicone.
• It does not have PTFE (Teflon).
• It doesn’t contain graphite or molybdenum disulfide.
• It is not water-based.
• It contains no chlorinated solvents, which makes it safer for plastics and electronics.

When people ask what’s in WD-40, they’re sometimes surprised at how simple the answer is: it’s mostly light solvents and light oils. No magic, just chemistry.