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How to Make the Best Penetrating Fluid | Liquid Wrench Alternative

Traditional penetrating fluids like Liquid Wrench, PB Blaster, WD-40, and Kroil have been widely used for years. However, there’s a cheaper and more effective alternative that has been around even longer.

In my search for an affordable penetrating fluid that could quickly loosen stubborn, corroded, or rusty nuts and bolts, I discovered a homemade solution that outperforms the off-the-shelf options.

While many garages use store-bought penetrating fluids, most people are unaware of this simple yet significantly more powerful penetrating fluid.

WD-40 and other products have their merits, but this homemade mix of automatic transmission fluid (ATF) and acetone works wonders against tough corrosion. It consistently outperforms commercial options in tests and is the most cost-effective choice.

Proof Homemade Penetrating Oil is Better (and it costs less)

Here is some proof to those claims:

Penetrating Oil Comparison Machinist Magazine April 2007
Penetrating Oil Comparison – Machinist Magazine April 2007

and if that wasn’t enough here is some more proof by Project Farm:

Project Farms results were a bit different showing that liquid wrench was top dog (just under good old high heat) but maybe that was due to using a different brand of synthetic ATF in their homemade penetrating oil. Others who used Valvoline Max Life full synthetic seemed to have better results than liquid wrench.

So as you can see, these results don’t lie, using the homemade penetrating oil mix beats the crap out of the competition cost-wise and performance wise (except in project farms case, but it was a close second).


A couple things I quickly noticed is you do not want to get the homemade penetrating oil mixture on your skin or eyes, and definitely do not swallow any of it. This is mostly due to the acetone, so please wear safety glasses and gloves that won’t be eaten by the acetone.

Acetone is also very flammable, keep any open flames away from acetone, the flame does not need to make contact with the acetone liquid to ignite, the vapors alone are enough to cause the acetone to ignite as seen in this video.

Acetone can cause lung irritation and tightening of the chest. Use in an open environment or well-ventilated area with a proper facemask.

When making this mixture do not use solo cups unless you will be transferring acetone out of the cup immediately. I found out the hard way.

Use either a glass bottle, steel can, container made out of Polypropylene (PP) plastic or high-density polyethylene (HDPE) plastic. Basically for those last two just check to see if the plastic container you want to use has HDPE or PP near the recycling logo on the bottom of the container, if it does your good to go as the acetone does not eat through this type of plastic.

If you want to make this homemade penetrating oil mixture yourself please read this disclaimer:

I am not responsible in any shape or form if you harm yourself while mixing or using this product. Mix and use at your own risk. Take all safety precautions necessary.

Now that we have the legalities out of the way here is the mixture.

Homemade Penetrating Oil Mixture Ratio

1:1, yup that simple. 1 part acetone and 1 part ATF. The type of ATF does not matter too much in my experience. Although I did see some arguments during my research that synthetic ATF was better since it penetrates into the corrosion better, I did not use synthetic myself and I had great results.

I just used regular ATF and after letting it sit on stubborn bolts for a few minutes they came off no problem.

To make it easier to use I just made the homemade penetrating oil mixture in a sealed oiling can. Give it a shake before use as the liquids will separate over time and spray whatever I need to break loose about 15 minutes before putting a wrench on it if I think it’s going to be stubborn. If it’s a really stubborn item like ball joints, try to spray it a day before you do any work.

oiling can
Oiling Can

I myself have not done an extensive comparison test between the off the shelf products and the homemade penetrating oil. I have used Pb Blaster, WD-40 and the homemade penetrating oil mixture though, so I can without a doubt say that the homemade penetrating oil mixture of ATF and acetone does a far better job breaking free stubborn bolts and nuts.

Not only does it take much less force to loosen rusted bolts and nuts after spraying with homebrew mixture but it works much faster as well.

Here is a list of the supplies I used to make my own ready to use homemade penetrating oil:

1: Oiling Can
2: Acetone
3: Automatic Transmission Fluid

What is your favorite penetrating oil? Have you used the homemade penetrating oil mixture of ATF and acetone before? If not, will you give it try? Leave your comments below.

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