Kroil vs PB Blaster vs WD-40: What the Makers’ Data Actually Shows

Kroil and PB B’laster are both petroleum-based penetrating oils made to creep into rusted threads and free seized parts; WD-40 Multi-Use Product is a general-purpose blend that lists penetration as one of several jobs. So for a rusted bolt, the real comparison is Kroil vs PB Blaster, with WD-40 as the multi-use can you may already own. Below is what each manufacturer actually publishes, plus the torque test everyone quotes and why we label it unverified.

Side by side: what the manufacturers publish

Point	Kroil Original Penetrant (Kano Laboratories)	PB B’laster Penetrant (B’laster)	WD-40 Multi-Use Product
Maker’s description	Penetrating oil that loosens rusted nuts and bolts, frozen shafts and pulleys	Penetrant that frees rusted or frozen parts and leaves a non-evaporating lubricant	Blend of lubricants with anti-corrosion, penetration, water-displacement and soil-removal ingredients
Base	Petroleum: severely hydrotreated distillates (30–50%) and LVP aliphatic hydrocarbon (20–40%), per Kano’s SDS	Petroleum, per B’laster’s technical data sheet	Contains petroleum distillates, per WD-40 Company
Flash point	132°F (55.5°C), liquid, per Kano’s SDS	150°F (66°C), per B’laster’s TDS	Not compared here; see the product SDS
Suggested soak	15–30 minutes to start; several hours or overnight for heavy corrosion	Saturate, let sit a few minutes, tap the part lightly; reapply on heavy corrosion	No dedicated soak guidance; WD-40 Company sells a separate Specialist Penetrant for stuck parts
Formats	8 oz drip bottle, 1 gallon can, 10–16.5 oz aerosols (AeroKroil)	11 and 18 oz aerosols, 4 oz trial size, 1 gallon and bulk	Aerosol and non-aerosol trigger bottle

The torque test everyone quotes

The numbers on forums come from a test credited to Machinist’s Workshop magazine; reposts usually date it to 2007. We could not find the original article, so the figures below are reported, not verified. They are copied from hobby-site and forum reposts, which don’t even agree on the unit (some say pounds, others foot-pounds), and none of them give the bolt size, how the rust was created, the soak time or the number of trials.

Treatment	Reported average force to loosen the nut
No penetrant	516
WD-40	238
PB Blaster	214
Liquid Wrench	127
Kano Kroil	106
Automatic transmission fluid + acetone, 50/50	53

Read it as one informal data point. In that single test every treatment beat a dry bolt, both dedicated penetrants needed less force than WD-40, and Kroil needed less than PB Blaster. The home mix of transmission fluid and acetone scored lowest of all, but we don’t recommend it: acetone is highly flammable, and a homemade blend has no label or safety data sheet to guide safe handling.

How each one works on the job

Kroil

Kano says Kroil works by capillary action: low surface tension lets it flow into the microscopic gaps between corroded surfaces, where it displaces moisture and leaves a thin lubricating film. It does not dissolve rust; it gets around and under it so the part turns with less force. Kano’s directions are to wet the threads and visible corrosion, wait 15–30 minutes, and on long-seized parts apply a second coat and wait several hours or overnight before applying steady pressure. Kano adds that working the fastener back and forth while it’s still wet often breaks the bond.

Kano rates Kroil safe on steel, iron, aluminum, brass, copper and most alloys, and generally safe on most plastics and painted surfaces, with a caution that prolonged contact can soften or swell some plastics and rubbers. For rubber seals and plastic parts Kano points to SiliKroil instead. Liquid Kroil is listed in NSF’s Nonfood Compounds program as H2 (Reg. #165745): it may be used in food plants only where there’s no possibility of food contact.

We carry Kroil KL081 Original Penetrating Oil in an 8 oz drip bottle, the Kroil KL011 1 gallon can for soaking parts in the shop, the KS162 AeroKroil 16.5 oz aerosol for overhead and spot work, and SiliKroil SK102 penetrant with silicone. To pick a format, see our AeroKroil vs SiliKroil vs liquid Kroil guide.

PB B’laster

B’laster’s technical data sheet describes an orange, petroleum-based penetrant with a pinpoint spray and a stated temperature range of -20°F to 300°F. Its directions are short: shake well, saturate the area, let it sit a few minutes and tap the part lightly to speed things up; on heavily corroded parts, spray again. The aerosol is classified as a flammable aerosol on its SDS. We don’t sell PB B’laster; it’s here because it’s the comparison buyers ask about most.

WD-40 Multi-Use Product

WD-40 Company says the name stands for Water Displacement, perfected on the 40th try, and describes the product as a blend of lubricants with anti-corrosion agents and ingredients for penetration, water displacement and soil removal. It’s handy for a lightly stuck hinge or for chasing water off tools. For seized fasteners, WD-40 Company itself offers a separate product, WD-40 Specialist Penetrant, so “Kroil vs WD-40” is really a specialist compared with a generalist.

Which one should you reach for?

• Rusted fasteners you can leave to soak: a dedicated penetrant and patience. Dwell time matters as much as the brand; Kano’s own guidance runs up to overnight for heavy rust.
• A lightly stuck part or water on tools: a multi-use product is enough.
• Near rubber seals or plastic: test on a hidden spot first; Kano suggests SiliKroil for rubber and plastic components.
• Food processing areas: none of the three is NSF H1. Liquid Kroil is H2, for areas with no possibility of food contact.
• Heat: Kroil and PB B’laster are flammable per their SDSs, and WD-40 contains petroleum distillates. Never use a torch on a part that’s wet with penetrant, and read the label and SDS before you start.

Frequently asked questions

Bottom line

Kroil and PB B’laster are purpose-built penetrants; WD-40 Multi-Use Product is a generalist. The one popular head-to-head number set favors Kroil, but it’s an unverified magazine test passed around online, so don’t buy on it alone. What you can count on: give any penetrant time to work, reapply on stubborn parts, keep it away from flame and check the SDS. Browse all penetrating oils or the full Kroil line, read what Kroil is used for, and find every SDS on our technical documents page.

Sources

• Kano Laboratories, Kroil Original Penetrant product page and FAQ: kroil.com
• Kano Laboratories, Kroil liquid Safety Data Sheet (9/2025): PDF
• NSF Nonfood Compounds Registration Program, certificate for Kroil, category H2, Reg. #165745: PDF
• B’laster, PB B’laster Penetrant product page: blasterproducts.com
• B’laster, PB Penetrant Catalyst technical data sheet (updated 5/10/2021): PDF
• B’laster, PB Penetrating Catalyst aerosol SDS: PDF
• WD-40 Company, History: wd40.com
• WD-40 Company, Myths, Legends and Fun Facts: wd40.com
• WD-40 Company, WD-40 Specialist Penetrant: wd40.com
• Machinist’s Workshop penetrating oil test, as reposted (reported, original not verified): vintagehydroplanes.com

Products in this guide