Best Penetrating Oil for Rusted Bolts: What Six Independent Tests Actually Agree On
Project Farm ran a four-video torture test. A machinist magazine ran the numbers in 2007. A sailing magazine tested on real corroded trailer hardware. And thirty years of forum mechanics have strong opinions. Here's where they agree, where they flatly contradict each other — and what freed the rusted bolt in my own garage.
By [AUTHOR NAME]·9 products compared·4 measured tests cited
Published: [DATE]Re-checked: [DATE] — all 9 products confirmed still soldMy own test: [pending / DATE]
Heads up: some links below are affiliate links — if you buy through them I earn a commission at no cost to you. As an Amazon Associate I earn from qualifying purchases. Every verdict here cites its source; nobody paid to be in this guide.
The short answer: for one can that does everything well, buy Seafoam Deep Creep — it won Project Farm's toughest single round outright and held up across his entire series. If you want the cheapest can that actually works, Liquid Wrench won his first test while costing the least. The enthusiast sleeper the forums swear by is Free All. And the honest fine print: in every measured test, heat and time beat every product on this page.
Your photo goes here
Hero shot: the three winners standing on your workbench next to the rusted hardware you'll test them on. Your hands in frame. This photo is the single strongest trust signal on the page — it proves a person with a garage wrote this, not a content mill.
What I own vs. what I researched
Fill in honestly — this box is load-bearingI own and have used: [e.g., PB B'laster (three cans over the years), Liquid Wrench, WD-40 Specialist...] I bought for this guide's test: [the 5-can test batch — list them] Researched only (sources cited inline): [e.g., Gibbs, Mouse Milk...]
Never claim hands-on for a product you haven't touched — the whole guide's credibility rides on this box being true.
How this guide decides
No single test settles this category, so this guide scores the consensus across every measured source I could verify, then adds what I see in my own garage:
Project Farm's four-video series (2018–2019, ~3.9M subscribers) — rusted ½-inch grade-8 wheel studs, breakaway torque measured with a digital torque adapter, all products self-purchased. His own disclaimer: the videos are "only for entertainment purposes" — he'd be the first to tell you it's one man's rig, not a certified lab. That honesty is why his numbers are worth citing.
Machinist's Workshop magazine (April 2007) — the oft-quoted torque test that made the ATF/acetone home brew famous. One small hobbyist test, endlessly re-circulated; cited here with that caveat attached.
Practical Sailor's "Rust Busters" (2009, updated 2020) — real corroded trailer U-bolts and abandoned machinery, where PB Blaster took the win.
Forum consensus — GarageJournal, TractorByNet, Yesterday's Tractors, and OPE Forum threads spanning two decades of professional wrenching.
My own test — [PLACEHOLDER: your 5-can breakaway test on matched rusted bolts, with photos and numbers]
The consensus table
Product
Project Farm's series
Other tests & the forums
My take
Seafoam Deep Creep
Won Ep. 2 outright (115.0 ft-lbs avg vs 131.6 untreated); finale: best all-rounder, third at pure unseizing
GarageJournal: "nearly as effective as ATF/acetone but aerosol-convenient"
[YOUR NOTE]
Liquid Wrench
Won Ep. 1 (97.3 vs dry 125.9); finale runner-up at 1 hr and 24 hrs
TractorByNet: "almost as good as Kroil for 20% of the price"; bulk buyers under $3/can (2022 thread)
[YOUR NOTE]
Free All
Runner-up to Gibbs in Ep. 3
GarageJournal: "better than Kroil and PB Blaster"; rarely in big-box stores
[YOUR NOTE]
Gibbs
Series finale winner — best pure unseizing at 1 hr (145.5) and 24 hrs (134.6, vs control ~167)
Niche availability; little forum coverage
[YOUR NOTE]
Kano Kroil
Dead last in Ep. 1 (124.6 — barely better than nothing)
The forum king — most-praised penetrant on GarageJournal & TractorByNet for decades; price revolt since 2022 (~$35/can peaks; gallons direct are the workaround)
[YOUR NOTE]
PB B'laster
Mid-pack Ep. 1 (122.0)
Won Practical Sailor's test; the accessible workhorse; the smell is infamous — a new Clear Low Odor variant exists because of it
[YOUR NOTE]
WD-40 Specialist Penetrant
Worst measured result in the series — Ep. 2 avg 136.0, above the untreated control (131.6) in a 1-hour test
Not classic WD-40 — a different formula; safe-on-plastics claim is its real niche
[YOUR NOTE]
CRC Knock'er Loose
Close 2nd in Ep. 2 (115.9)
GarageJournal: "reminds me a lot like Kroil" at a third of the price; a freeze-shock "Plus" variant exists
[YOUR NOTE]
ATF/acetone 50-50 mix
Mid-pack Ep. 1 (114.1)
Won the 2007 Machinist's Workshop test (53 ft-lbs vs Kroil's 106, WD-40's 238, and 516 with nothing) — one old test, huge folk reputation
[YOUR NOTE]
All Project Farm figures are average breakaway torque in ft-lbs, read from his on-screen results charts, cited with permission-free factual attribution: Ep. 1 · Ep. 2 · Ep. 3 · Finale. Lower is better; each episode used a different torque preload, so compare within a row's episode, not across episodes.
The Kroil problem: when the lab and the forums disagree
Direct answer: Kroil is the most-recommended penetrating oil on every major wrenching forum — and it finished dead last in Project Farm's first measured test, barely beating bare rust. Both things are true, and the disagreement is the most useful fact in this category.
Project Farm's Ep. 1 gave every product three applications over three hours on lab-rusted studs. Kroil's reputation was built somewhere else entirely: decades of overnight soaks on farm equipment, aircraft, and machine tools — long-duration creep on real-world corrosion. A three-hour test measures speed; the forums are grading patience. His own series backs the distinction: every product improved when the finale re-tested at 24 hours instead of one.
What this means for your wallet: if you spray and wrench within the hour, the measured tests say buy Seafoam, CRC, or Liquid Wrench. If you can soak overnight, the Kroil faithful may have a point — but at 2022-era prices (a GarageJournal thread titled "Kroil Is Too Damn Expensive!" says it all), Liquid Wrench at a fraction of the cost is where value lands.
Your test slot This is the exact conflict your own 5-can test resolves: same bolts, 1-hour AND 24-hour rounds. Whatever you find, you'll have the only page on the internet that tested the disagreement directly.
The cheap trick: does the ATF/acetone mix really beat everything?
Direct answer: it won the one magazine test everyone quotes (2007), finished mid-pack in Project Farm's bigger 2018 test, and comes with real handling downsides no aerosol has. Great backup, questionable daily driver.
The legend comes from Machinist's Workshop (April 2007): a 50/50 mix of automatic transmission fluid and acetone needed just 53 ft-lbs of breakaway torque against Kroil's 106 and untreated hardware's 516. Those numbers are real — and they're also a single small hobbyist-magazine test that's been recirculated secondhand for nearly twenty years. (You'll see those figures wrongly credited to Project Farm all over the internet; his test is a different one with much smaller spreads.)
The caveats mechanics themselves raise: the mix separates fast (shake constantly), acetone attacks paint, rubber, and nylon-insert nuts, it evaporates quickly so you mix fresh each use, and it's very flammable. Project Farm's own warning is worth quoting: "Acetone is a pretty harsh chemical and it can do damage to vehicle paint or to plastic or rubber parts."
What about plain WD-40?
Direct answer: classic WD-40 is not a penetrating oil, and the measured tests agree — it posted the worst product score in the 2007 magazine test (238 ft-lbs). The Specialist Penetrant is a genuinely different formula, but it produced the series' strangest result: in Project Farm's one-hour test it averaged slightly worse than using nothing at all.
One forum line sums up two decades of threads: classic WD-40 is "the best marketing for the worst product." Fair or not, if it's what's on your shelf, the data says add time — a lot of it — or walk to the store.
The honest section: heat and time beat everything in the can
Project Farm's torch beat every product in Ep. 1 (91.5 ft-lbs — better than the best oil). His finale showed every single product improving with 23 extra hours of soak time. And the most-repeated sentence across every forum thread I read: "the most important thing with any of these products is time." His conclusion is the right one: "Something is better than nothing. If you use any of these products, you're doing better than if you use nothing at all." Buy a good can — then give it the night, and keep a torch in reserve.
Stuck right now with a rounded or stripped head? A penetrant can't fix a fastener you can no longer grip — that's an extractor job. [INTERNAL LINK: → "How to remove a stripped bolt" · → "Best bolt extractor set"]
Common questions
How long should penetrating oil soak?
Longer than the label implies. In the only same-bolt comparison available (Project Farm's finale), every product freed bolts measurably easier at 24 hours than at 1 hour. Minimum: give it an hour and several re-applications. Ideal: overnight.
Is Kroil worth the money?
For overnight soaks on serious rust, its decades of professional word-of-mouth are hard to dismiss; for quick jobs, the measured tests say cheaper cans work as well or better. If you go Kroil, the gallon jug direct from the maker is the sane way to buy it. (Note: "AeroKroil" was renamed "Kroil Original Penetrant" in 2021 — same product line.)
What actually won the most tests?
No product swept. Liquid Wrench, Seafoam Deep Creep, and Gibbs each won a Project Farm round; the ATF/acetone mix won the 2007 magazine test; PB Blaster won Practical Sailor's. That's exactly why this page scores the consensus instead of crowning one can.