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 WD-40 has and hasn't freed for me at home.
Won Project Farm's one-hour round outright (115.0 ft-lbs vs 131.6 untreated). His finale called it the best all-rounder, third at pure unseizing.
For: one can that does everything well
Skip if: you only care about raw unseizing power. Gibbs beat it there
Check price on AmazonOutright winner of Project Farm's original test (97.3 ft-lbs against 125.9 dry); finale runner-up at one and 24 hours.
For: the glovebox and the just-in-case shelf
Skip if: you want maximum creep for overnight soaks
Check price on AmazonThe can veteran mechanics bring up unprompted. Runner-up in Project Farm's third round, and rarely on a big-box shelf.
For: stubborn rust when the usual cans have failed
Skip if: you need it today from a local store
Check price on AmazonI have not owned or bench-tested any can in the table below. The ranking is the cited testers' work: Project Farm, Machinist's Workshop and Practical Sailor, cross-checked against twenty years of forum threads. That is why no product here carries a "Bought at retail" label. The one can on my shelf is classic WD-40. The 2007 test gave it the worst product score in the field, and it still comes in handy very often at my house. It is the wrong can for a rusted bolt and the right one for a squeaky hinge.
What's on my shelf. WD-40 comes in handy very often, from squeaky doorknobs and hinges to anything else that decides not to move. Anything that makes noise gets a squirt. And yes, it definitely freed some tough screws.
When it wasn't enough. I have on many occasions fought with a stripped bolt. Most recently on my pool pump. I tried WD-40 and larger and larger screwdrivers, and ultimately had to break it and strip it out.
No single test settles this category, so this page scores where the measured sources agree, then adds what WD-40 has done for me at home. The sources:
| Product | Project Farm's series | Other tests & the forums |
|---|---|---|
| Seafoam Deep Creep Amazon | Won Ep. 2 outright (115.0 ft-lbs avg vs 131.6 untreated); finale: best all-rounder, third at pure unseizing | GarageJournal members put it close to the ATF/acetone mix, in an aerosol |
| Liquid Wrench Amazon | Won Ep. 1 (97.3 vs dry 125.9); finale runner-up at 1 hr and 24 hrs | TractorByNet members rank it just behind Kroil (2022 thread) |
| Free All Amazon | Runner-up to Gibbs in Ep. 3 | GarageJournal members rank it above Kroil and PB Blaster; rarely in big-box stores |
| Gibbs Amazon | Series finale winner — best pure unseizing at 1 hr (145.5) and 24 hrs (134.6, vs control ~167) | Niche availability; little forum coverage |
| Kano Kroil Amazon | Dead last in Ep. 1 (124.6 — barely better than nothing) | The forum king — most-praised penetrant on GarageJournal & TractorByNet for decades; since 2022 the forum complaint is what it costs; gallons direct from the maker are the workaround |
| PB B'laster Amazon | Mid-pack Ep. 1 (122.0) | Won Practical Sailor's test; the accessible workhorse; the smell is infamous, and a Clear Low Odor variant now exists |
| WD-40 Specialist Penetrant Amazon | 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 |
| CRC Knock'er Loose Amazon | Close 2nd in Ep. 2 (115.9) | GarageJournal members compare it to Kroil; a freeze-shock Plus variant exists |
| 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 |
All Project Farm figures are average breakaway torque in ft-lbs, read from his on-screen results charts: 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.
Project Farm's Episode 2: average breakaway torque after a single application and a one-hour soak. Shorter bar = bolt gave up easier.
ft-lbs to break the nut loose · gray = untreated control · two products measured worse than nothing in this short-soak test
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, slow 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 in practice: 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; the same forums that crown it now complain about what it costs, which is why Liquid Wrench is the pick here.
I have not run that test myself, and this page will not pretend otherwise. Treat the disagreement above as unresolved. The forums and the torque wrench are grading different exams.
The legend comes from Machinist's Workshop (April 2007, surviving via forum reprints). A 50/50 mix of automatic transmission fluid and acetone needed just 53 ft-lbs of breakaway torque. Kroil needed 106, and untreated hardware 516. Those numbers are real. They are also one small hobbyist-magazine test, and the mix has been winning that same 2007 test in forum posts ever since. You will 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 is 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."
Two decades of forum threads reach the same verdict on classic WD-40: great marketing, poor penetrant. Fair or not, it is what is on my shelf. Mine has freed some tough screws and lost to one pool pump, which is about what the numbers predict. If it is what is on your shelf too, the data says add time, a lot of it, or walk to the store.
Project Farm's torch beat every product in Ep. 1 at 91.5 ft-lbs, better than the best oil. The best penetrating oil in that round was fire. His finale showed every single product improving with 23 extra hours of soak time. And the sentence that comes up most in the forum threads 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.
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