Get The Fuck OutMaterials, Paint & AdhesivesATF + acetone penetrant

What's the cheapest penetrating oil that actually works?

Two things off the shelf at any auto store, mixed in a jar, and you've got a rust-buster that goes toe to toe with the expensive aerosol.

Acetone is highly flammable and its vapour travels. Mix small batches outdoors or with real ventilation, keep it away from any flame, spark, or hot work, store it in a sealed metal or acetone-safe container — never a soft plastic bottle — and label it. Wear gloves and eye protection.

⚡ Rule of thumb

Mix roughly equal parts automatic transmission fluid and acetone for a cheap penetrating oil — the acetone carries the ATF into the rust, then flashes off and leaves the oil behind.

Starting point

≈ 50:50 ATF to acetone by volume

Measured

By volume, mixed small and shaken before each use — it separates

Confidence

Widely accepted

▶ Source video — 8 Workshop Hacks — Alley Pickedwatch on YouTube ↗

Applies to

Process: Freeing seized and corroded fasteners
Materials: Rusted steel — bolts, clamps, hinges, linkages
Setup: ATF and acetone from an auto store, a sealed acetone-safe container
Not for: Painted surfaces, most plastics, or anything acetone attacks

Why it matters

Rust doesn't hold a bolt with glue, it holds it by filling every gap with expanded oxide. Getting anything into that gap is the whole problem, and a thick oil can't.

Acetone is thin enough to wick in and it carries the ATF with it. Then the acetone evaporates and leaves oil where nothing else could reach. The source clip shows it freeing a rusted C-clamp.

What good looks like

The mix visibly wicks into the joint rather than beading on it
It's given time — soak, tap the fastener, soak again
The container is sealed and labelled, and stored away from heat

How to apply it

Mix roughly equal parts ATF and acetone in an acetone-safe sealed container. Small batches — this is not a thing to make a litre of.
Shake before use; the two separate on standing.
Apply to the fastener and give it time. Tapping the head with a hammer helps it draw in.
Re-apply and wait again before you put a bar on it.

Exceptions & tradeoffs

Acetone attacks paint, many plastics, and some rubbers. Keep it off anything you care about the finish of.

Never use this anywhere near hot work. If you're about to heat a fastener with a torch, clean the penetrant off first and let it dry.

It separates in storage and the acetone will escape a loose lid. Seal it properly or make it fresh.

Common mistakes

Mixing a big batch and leaving it in a soft plastic bottleSmall batches, acetone-safe sealed container, labelled
Applying it and immediately putting a breaker bar on the boltGive it time to wick — that's the entire mechanism

Alley PickedSource & visual reference

Mixing roughly equal parts ATF and acetone as a cheap penetrating oil, shown freeing a rusted C-clamp — 8 Workshop Hacks ↗ at 0:40–1:45.

Summarized and independently edited by Start Here. The mix and the demonstration are the creator's. Every flammability, storage and material-compatibility caution on this page is ours, and they're not optional.