Over time, parts such as bolts, fasteners, and more can rust or corrode, eventually becoming nearly impossible to loosen. Penetrating oil lubricates even the stiffest, most stuck-together metal surfaces so they glide easily over each other. This tool is essential in every mechanic’s arsenal for its extensive versatility, whether it’s in the shop or for a DIY project.

We’ve rounded up and reviewed the best penetrating oils to help make your next engine repair go smoothly. We’ll discuss the pros and cons of each oil and delve into what customers thought of each, plus explain the essential features of penetrating oils.

5 Best Penetrating Oils

#1 Best Aerosol: Kano AeroKroil Penetrating Oil

Kano AeroKroil attacks corrosion to free bolts, nuts, and other mechanical parts from scraping. Its advanced formula prevents rust and carbon deposits from forming to create a long-lasting protective coat that keeps your engine properly lubricated.

Due to its aerosol can design, AeroKroil penetrates deeper into metal than liquid oils and is faster-acting, as well. This product works on rubber and plastic, so it won’t damage them if spilled in your engine.

Our Rating: 5 out of 5

What Customers Are Saying

Customers greatly admire the Aerokroil, scoring it an average rating of 4.9 out of 5 stars from nearly 2,000 reviews. Over 90 percent of all ratings are 5 stars, while less than 2 percent are 1-star scores.

Those who left positive reviews enthusiastically endorse the AeroKroil for how quickly it works after the first coat. Some customers note that a small amount of AeroKroil is enough to make a big impact on their engine.

While this product has mostly positive reviews, a couple of unsatisfied customers claim the AeroKroil did not loosen stuck bolts as well as they had hoped.

#2 Best Liquid: Liquid Wrench Penetrating Oil

Having been in the automotive oil industry since 1941, Liquid Wrench is a tried-and-true name with more experience than most brands. Their penetrating oil works on rusted nuts and bolts and can even remove excess adhesive from stickers or other glues.

Liquid Wrench can seep easily between corroded metals thanks to its low surface tension. It’s safe to use on painted surfaces, and it contains no volatile organic compounds (VOCs), improving its everyday use. The only drawback of this oil is that it comes in a relatively small canister, so one bottle must be used sparingly.

Our Rating: 4.9 out of 5

What Customers Are Saying

Liquid Wrench Penetrating Oil has over 200 reviews and an average rating of 4.6 stars. Almost 80 percent of reviewers left a rating of 5 stars.

Many customers appreciate the speed at which Liquid Wrench worked, citing less squeaky hinges and clean parts within a few minutes of using it. There are also customers who like using the squeeze bottle for more precise application.

There are very few negative reviews on Amazon for this product, but some express dissatisfaction with the Liquid Wrench bottle, saying the spout broke after a few uses.

#3 Best Multi-Spray Option: WD-40 Multi-Use Spray

Another trusted name, WD-40 can unstick most stuck nuts and bolts. Its formula acts as a corrosion inhibitor to block moisture and other damaging elements to prevent rust. Also, WD-40 doesn’t contain any silicone, kerosene, water, graphite, or chlorofluorocarbons (CFCs), so it’s healthier for both your engine and the environment.

With WD-40’s Smart Straw, automotive enthusiasts can choose between a wide spray for broad application or a direct stream better for precise lubricating. And as a multi-purpose oil, WD-40 can be used on almost any sticky or squeaky surface.

Our Rating: 4.9 out of 5

What Customers Are Saying

Reviews for this WD-40 spray on Amazon have an average rating of 4.7 stars. This is from over 500 reviews, over 90 percent of which are 4 stars or higher.

A majority of customer reviews recommend WD-40 spray as a must-have for both automotive and household use. There are also numerous reviews praising this product for how well it works on door hinges.

On the other hand, some customers found the Smart Straw ineffective for getting into hard-to-reach places.

#4 Best Rust Remover: B’laster PB Penetrating Catalyst

B’laster PB Penetrating Catalyst has a non-evaporating formula that leaves behind a layer of protection against rust. Because of its low viscosity, this oil can reach between tight crevices with ease to break down corroded or rusted engine pieces.

Beyond cars, this penetrating oil also works on industrial, marine, plumbing, and other equipment. PB B’laster oil loosens frozen parts, which makes it ideal for quick fixes in cold weather areas.

Our Rating: 4.8 out of 5

What Customers Are Saying

From around 600 ratings, the PB B’laster has an average rating of 4.7 stars. Only about two percent of all customers left a score of 2 stars or lower, while more than eighty percent left 5-star ratings.

Some customers recommend allowing the PB B’laster to sit for a few hours to a day before wiping to obtain the best results against rust. Others believe that warming up parts and then spraying improves its performance.

Negative reviews say the PB B’laster’s spray straw clogs easily.

#5 Best Straight Oil: Gasoila Free All Deep Penetrating Oil

Gasoila Free All Deep Penetrating Oil targets rust, corrosion, and adhesives with pinpoint accuracy. Its penetrating fluid can unstick screws, nuts, bolts, and clamps as well as moving parts such as universal joints and locks.

This oil contains no silicone additives, so it won’t damage any paint it may come in contact with. It doesn’t dry quickly, either, so only one or two coats and patience are required to watch the Gasoila go to work.

Our Rating: 4.7 out of 5

What Customers Are Saying

Nearly 3,000 customers reviewed this product on Amazon, giving it an average rating of 4.6 stars. About 90 percent of customers left a rating of 4 stars or higher.

Those who admired the Gasolia had positive things to say about how quickly it worked. Some reviewers mentioned that it works especially well for loosening grinding gears.

While many positive reviews said the Gasoila worked quickly, there were negative reviews that claimed the opposite, citing wait times of up to a few hours before seeing results.

Best Penetrating Oil Buyers Guide

Whether it’s loosening rusted bolts or declogging a cluttered pipe, choosing the right penetrating oil is vital to your vehicle’s performance. Be sure to understand what works best for your engine before deciding on any oil products.

Different Types Of Penetrating Oils

  1. Synthetic: These do not contain petroleum or mineral oils. Although more expensive than other oils, synthetic penetrating oils are fire-resistant and can act as a superb coolant.
  2. Straight: These are generally petroleum-based or vegetable oils that don’t contain water. These are used more frequently for metal surfaces where lubricity is more important than heat reduction.
  3. Water-soluble: Unlike the first two oils, these have a high water content and can be diluted in water for low concentrations. Water-soluble oils are generally reserved for parts that can be easily corroded by harsh solvents in some synthetic and straight oils.

Benefits Of Penetrating Oil

  • Lubrication: Many penetrating oils lubricate metal parts. This reduces friction and loosens stuck or tightly-wound nuts and bolts. Usually, this is only a temporary fix but sometimes it can be long-lasting.
  • Corrosion-resistance: Penetrating oils are designed to prevent metal surfaces from corroding. Over time, corrosion can significantly weaken metal, and oils displace moisture that can eventually lead to rust.
  • Cleaning agents: Most penetrating oils can remove adhesives, tar, and more from metal surfaces. They can dissolve debris so they can be wiped away using a light abrasive such as a cloth or wipe. The best oils should also act as a rust penetrant and have water solvent properties to prevent rust buildup.
  • Noise reduction: When metal surfaces corrode, they can produce awfully loud creaking and squeaking noises. Since penetrating oil prevents them from rubbing against one another, an additional benefit is that they reduce noise.

Our Review Standards

To select the five oils in this review, our team searched Amazon and Advance Auto Parts for top products, looking at factors like customer ratings, price, superlatives, and Prime shipping eligibility.

Frequently Asked Questions

*Data accurate at time of publication.