The Best Penetrating Oil for Plumbers

Sometimes, elbow grease isn't enough to get the job done and you need a quality penetrating oil to loosen stubborn problems. Penetrating oils work on rusted bolts on pipe fittings, valves, and connectors, free stuck shower heads or faucets, and prevent future seizing on threaded parts like hose bibs, sink handles, and sprinkler heads. With so many options out there, we’ve rounded up the top 6 choices, all trusted by professional plumbers.

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1. Liquid Wrench
2. Royal purple
3. WD-40
4. PB Blaster
5. Kroil
6. CRC Knock’er Loose Penetrating Oil

1.Liquid Wrench — Penetrating Oil

The owners of Liquid Wrench are pretty proud that they're still a family-run business, after a whopping 75 years developing specialty lubricants and greases. Made in the USA, their products are all about staying innovative and keeping things local. Their signature penetrating oil regularly tops review lists and comparisons of penetrating oils for its performance, often also at a fraction of the price of its main competitors. Its top qualities are that it has a subtle odour, 0% VOC, is 50-state compliant and is safe on painted surfaces, plastic & PVC!

2. Royal Purple — Maxfilm High-Performance Multipurpose Synthetic Penetrating Spray

Royal Purple Maxfilm is one of the most effective multipurpose penetrating oils on the market. Its high film strength and synthetic formula, along with its non-petroleum CO2 propellant, provide a more eco-friendly option without sacrificing performance. One of its standout features is its ability to provide long-term lubrication. Many users find that the quality of the lubrication improves over time as the solution settles into every crevice, rather than evaporating. This allows it to deeply penetrate and loosen rusted or stuck components like nuts, bolts, locks, and hinges!

3. WD-40 — Specialist Silicone Lubricant

It's what your dad used, it's what your grandmother used, it's what her parents used. Since 1953, WD-40 has been the go-to lubricant for homeowners, plumbers and professionals. Its triple-action formula not only loosens and lubricates metal but also protects against natural elements like moisture, leaving no sticky residue—just a clear, quick-drying protective film. Although not ideal for heavy-duty applications, it remains a go-to option for light lubrication and rust prevention.

4. PB Blaster — Penetrating Catalyst

For the best balm for your buck, PB Blaster is an incredibly effective penetrating oil at an unbeatable value."Often compared to WD-40, PB Blaster's penetrating oil is a quality, rust-resistant lubricant. Users also note that, unlike many competitors, the built-in straw ensures the red tube won’t be lost. However, some have pointed out that the product’s cost-saving benefits come with a few downsides, such as a much stronger odour. Additionally, some users feel it dries too quickly for their liking. It should also be handled with caution due to its hydrocarbon base, which can be flammable and will require proper ventilation during use.

5. Kroil — Original Penetrating Oil

Karoil's Aerokroil Penetrating Oil, the most premium option on this list, is popular for displacing water, providing lubrication, and preventing rust. It excels at removing grease, grime, gum, tar, and sap while dissolving dried grease — without damaging metal. Customers report that it penetrates deeply and often outperforms products like WD-40, in particular for long-term lubrication. However, its high price and strong odour are common drawbacks. Despite this, Aerokroil is an excellent choice for tough mechanical tasks and long-term rust prevention.

6. CRC — Knock’er Loose Penetrating Solvent

CRC Industries Knock’er Loose is a penetrating solvent formulated to dissolve rust, scale, gum, grease, and corrosion, making it ideal for removing and preventing rust buildup. It’s best suited for heavy-duty applications, offering plumbers a reliable solution for challenging repairs such as seized fittings, corroded bolts, and stuck valves. While the solution excels at penetrating rust buildup, it may require several applications, and in some cases, days of regular use to fully seep through.

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