Can WD-40 Be Used As Starting Fluid? (Explained)

WD-40 has earned a reputation as a multi-purpose product, and in some cases, it’s even used to help start engines. If your car refuses to start and you’re out of traditional starting fluid, spraying a short burst of WD-40 into the air intake can sometimes get the engine to fire.

That’s because WD-40 is flammable. It contains hydrocarbons that can ignite inside the combustion chamber, helping kickstart the engine. While it’s not made for this purpose, many mechanics and car owners have used it as a quick workaround—especially when ether-based starter spray isn’t available.

Still, it’s important to understand that WD-40 isn’t a proper substitute and should only be used occasionally, not as a long-term solution.

What Is Starting Fluid, Really?

Starting fluid is a fast-evaporating, highly flammable aerosol designed to help internal combustion engines start—especially in cold weather or when there’s a problem with fuel delivery or ignition.

Most starting fluids use ether as the main ingredient. Ether ignites easily, even in freezing temperatures, which makes it ideal for difficult starts. When sprayed into the air intake, it helps create immediate combustion in the cylinders, giving the engine a quick boost.

While effective, starting fluid isn’t something you want to rely on regularly. It’s a diagnostic tool and emergency aid—not a solution. Overusing it can cover up deeper problems like weak fuel pressure, bad sensors, or poor compression. And since ether strips away oil from cylinder walls, excessive use can actually harm the engine over time.

How to Use WD-40 as a Substitute for Starting Fluid

If you’re using WD-40 to help start your engine, the process is similar to how you’d use traditional starting fluid. Just keep in mind this is a backup method—not a replacement for proper diagnostics.

Here’s how to do it:

1. Check your vehicle’s manual first. Some manufacturers specifically warn against using any kind of starting fluid.

2. Pop the hood and locate the air intake. You may need to remove the air filter for direct access.

3. Hold the WD-40 can a few inches from the intake and give it a 2–3 second spray.

4. Reinstall the air filter, then get in and turn the key or press the start button.

If the engine fires up, it likely means your ignition and compression are fine—but fuel delivery may be weak. If it doesn’t start, you can try spraying again once or twice. If it still refuses to run, the issue likely goes beyond fuel or spark, and it’s time for a deeper mechanical check.

Does WD-40 Contain Ether?

No—WD-40 does not contain ether, which is the main ingredient found in most starting fluids. Ether is extremely volatile and ignites almost instantly, which is why it works so well in cold-start situations.

WD-40 relies on different flammable ingredients—mainly hydrocarbons like propane, butane, and aliphatic solvents. These can still combust in the engine, but they don’t burn as aggressively or reliably as ether.

It’s also worth noting that older versions of WD-40 used flammable propellants like propane. Many newer cans now use carbon dioxide (CO₂), which doesn’t aid combustion at all. So depending on the version you’re using, the flammability—and effectiveness as a starting aid—may vary.

Is WD-40 Better Than Starting Fluid?

Some people claim WD-40 is better than traditional starting fluid because it doesn’t dry out the engine. And there’s a little truth to that—starting fluids that rely on ether can strip away oil from the cylinder walls, especially if overused. That’s not ideal for engine longevity.

WD-40, on the other hand, contains light oils and lubricants. It won’t dry out internal components the way ether can. But that doesn’t automatically make it better.

Here’s the trade-off:

• WD-40 doesn’t ignite as easily, especially in cold weather.

• Its flame front is slower and less consistent.

• It wasn’t designed to assist combustion—just to displace moisture and lubricate metal.

So while WD-40 is less harsh on your engine, it’s also less effective as a starting aid. In a pinch, it can help. But for reliable cold starts or serious diagnostic work, ether-based starting fluid still does the job better.

Why Do People Use WD-40 Instead of Starting Fluid?

It mostly comes down to availability. Not everyone has starting fluid sitting on a shelf, but WD-40 is common in most households and garages. So when a cold-start issue pops up, WD-40 becomes the go-to out of convenience.

It’s not about performance—it’s about what’s within reach. WD-40 is a multi-purpose product, and in emergency situations, it’s often the only thing handy that’s even remotely flammable and safe to try.

But that doesn’t mean it’s better. It just means it’s there when you need something in a pinch.

What’s the Difference Between WD-40 and Starting Fluid?

While both products can help start an engine, they’re built for completely different purposes.

Starting fluid is designed to ignite instantly and help engines fire up during cold starts or when fuel delivery is weak. It’s typically made with ether and meant to be sprayed into the intake just before cranking the engine.

WD-40 is a lubricant and moisture displacer. It was never designed to aid combustion. Its flammability is more of a byproduct than a feature. It burns slower and is less consistent than starting fluid when it comes to cold ignition.

The bottom line is that just because both can start an engine doesn’t make them interchangeable. Use WD-40 only as a backup—not a long-term replacement.

What About Carb Cleaner?

Carburetor cleaner is another product that can help in a pinch. It’s designed to remove carbon and varnish from carburetors, but since it contains flammable solvents, it can also ignite inside the combustion chamber—making it a viable starting fluid substitute.

While it’s not as volatile as ether, it generally works better than WD-40 at starting engines, especially in cold conditions. Just be careful—some carb cleaners can be harsh on rubber seals or plastic components if overused.

Interestingly, WD-40 can also act as a light-duty carb cleaner, especially for breaking up mild deposits without damaging softer materials. It’s not as aggressive as a true carb cleaner, but it’s safer on sensitive parts and wiring.

Will WD-40 Damage My Engine?

Used occasionally and in small amounts, WD-40 won’t damage your engine. In fact, it can help clean carbon buildup and displace moisture from spark plugs, wires, and other components.

It also leaves behind a thin film of lubricant, which is far less harsh than ether-based starting fluids that dry out cylinder walls. That said, it’s not designed to be sprayed into the intake regularly.

If you overuse it, you risk building up residue that can foul sensors, coat plugs, or interfere with proper combustion over time. So while it’s safe for a one-time cold start, it’s not something you should rely on often.

What Are Some Alternatives to Starting Fluid?

If you don’t have starting fluid or WD-40 on hand, there are a few other options that can help get a stubborn engine running:

• Premixed 2-stroke fuel – Used in chainsaws and lawn equipment, this fuel contains oil and gasoline in the right ratio to lubricate while it ignites. It’s one of the safer and more effective alternatives.

• Carburetor cleaner – As mentioned earlier, it’s flammable enough to work as a starter in a pinch and burns more cleanly than WD-40.

• Throttle body cleaner or brake cleaner – Some formulations are flammable and can help in emergencies, but use with caution. Many of these sprays are harsh and not designed to be pulled into the combustion chamber.

Avoid using random household sprays or unapproved chemicals. If you’re unsure what’s in it, don’t put it in your engine. And remember—if your engine constantly needs a boost to start, it’s time to address the root cause. Relying on quick fixes might get you running, but it won’t keep you there.