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Loading...Thirty half-inch grade 8 wheel lug studs were rusted to order rather than scavenged, so that every fastener started from the same place: acid stripped the zinc plating, then an oxidizer was applied with the studs standing vertically so it ran down the threads evenly. Lug nuts went on bevelled end down, keeping the contact area small and consistent, and each was torqued to 100 ft-lbs. Four studs were then broken loose dry to set the baseline, six treatments were applied to four studs each, re-dosed after an hour and left to soak for about three hours, and two studs were held back for a torch.
Price and performance ran in opposite directions here. The $4 can finished first, ahead of the $13 and $15 cans, and a one-to-one mix of acetone and automatic transmission fluid — ingredients already sitting on most shop shelves — came second. The more useful finding sits underneath the ranking: every one of the six treatments broke its nuts loose more easily than the untreated studs did, so reaching for any of them beats reaching for none.
Best Overall
First of six on rusted grade 8 lug studs, and the least expensive can in the test at $4
Purchased for: $4
The least expensive can in the test at $4, advertised to dissolve rust and cut through grease. An hour after the first dose, most of what had been sprayed on had either soaked into the threads or flashed off, leaving the studs looking much like the Aero Kroil ones. It finished first of the six treatments on the rusted grade 8 studs.
Best Home Brew
One part acetone to one part ATF, finishing second ahead of four commercial penetrants
A home brew of one part acetone to one part synthetic automatic transmission fluid, mixed fresh for each dose. It was the only treatment still visibly wet an hour in — the transmission fluid stays on the threads and keeps working its way down — and it finished second overall. Acetone is harsh enough to damage vehicle paint, plastic and rubber, and it soaks through some glove materials, so it wants care and ventilation.
Biggest Surprise
Fourth of six, despite being sold as a water displacer rather than a dedicated penetrant
Water Displacement formula 40, sold as a lubricant, a rust protector, a penetrant and a water displacer rather than as a dedicated penetrant. It was the slowest of the group to evaporate, with plenty still visible on the threads an hour after spraying. Fourth of six, ahead of both PB Blaster and Aero Kroil.
Check out these related product tests
| Name | Purchased for ($) | Link | |
|---|---|---|---|
| Liquid Wrench | $4.00 | Search on Amazon | |
The least expensive can in the test at $4, advertised to dissolve rust and cut through grease. An hour after the first dose, most of what had been sprayed on had either soaked into the threads or flashed off, leaving the studs looking much like the Aero Kroil ones. It finished first of the six treatments on the rusted grade 8 studs. | |||
| Acetone/ATF Mix | $ | ||
A home brew of one part acetone to one part synthetic automatic transmission fluid, mixed fresh for each dose. It was the only treatment still visibly wet an hour in — the transmission fluid stays on the threads and keeps working its way down — and it finished second overall. Acetone is harsh enough to damage vehicle paint, plastic and rubber, and it soaks through some glove materials, so it wants care and ventilation. | |||
| Royal Purple Max Film | $13.00 | Search on Amazon | |
A synthetic penetrant and lubricant at $13 a can, sold on wear protection, rust and corrosion prevention, and loosening rusted and stuck parts. More of it was still sitting on the threads and the nut at the one-hour check than PB Blaster. Third of the six treatments, which is a lot of money for a third-place finish. | |||
| WD-40 | $ | Search on Amazon | |
Water Displacement formula 40, sold as a lubricant, a rust protector, a penetrant and a water displacer rather than as a dedicated penetrant. It was the slowest of the group to evaporate, with plenty still visible on the threads an hour after spraying. Fourth of six, ahead of both PB Blaster and Aero Kroil. | |||
| PB Blaster | $ | Search on Amazon | |
Advertised as the number one selling penetrant, claiming to break free rusted and frozen parts, to protect against further rust and corrosion, and to attack rust from all angles through capillary action. It was the driest of the group at the one-hour check, with noticeably less film left behind than Liquid Wrench or Aero Kroil. It placed fifth of the six treatments. | |||
| Aero Kroil | $15.00 | Search on Amazon | |
The most expensive can in the test at $15, and the one carrying the strongest reputation. It is sold as a lubricant, rust remover, cleaner and rust preventer, and claims to creep into openings as small as one millionth of an inch to free frozen metal parts. An hour after spraying, most of what had been applied had soaked into the threads or evaporated. It came sixth of the six on the rusted studs, still ahead of leaving the fastener dry. | |||
Lower is better
Prices at the time of testing, per can. Aero Kroil is the most expensive product in the group at $15, with Royal Purple Max Film at $13, against $4 for the Liquid Wrench that went on to finish first.
Finishing position across the seized-fastener testing, 1 through 7 — lower is better
Each treatment went onto four rusted grade 8 studs, was re-dosed after an hour and left roughly three hours before the nuts were broken loose, with four untreated studs run alongside as the baseline. Liquid Wrench finished first at $4 a can, the one-to-one acetone and ATF home brew second, and Royal Purple Max Film third at $13. Every treatment came out ahead of the untreated baseline, and the $15 Aero Kroil placed last of the six.
| Rank | Product | Result |
|---|---|---|
| 1 | Liquid Wrench | 1 |
| 2 | Acetone/ATF Mix | 2 |
| 3 | Royal Purple Max Film | 3 |
| 4 | WD-40 | 4 |
| 5 | PB Blaster | 5 |
| 6 | Aero Kroil | 6 |
| 7 | Untreated Control | 7 |
The pick for best overall is Liquid Wrench. It finished first of the six treatments on rusted grade 8 lug studs and it is also the cheapest can in the group at $4 — the opposite of what the price tags suggest should happen, given that the $15 Aero Kroil placed last of the six and the $13 Royal Purple Max Film managed third. Nothing about how it sat on the threads at the one-hour check marked it out; it simply broke the nuts loose with less fight than anything else in the comparison.
The value story is the home brew. A one-to-one mix of acetone and synthetic automatic transmission fluid finished second, ahead of four commercial penetrants, and it was the only treatment still visibly wet an hour after the first dose while the aerosols had largely soaked in or flashed off — the transmission fluid keeps creeping down into the threads long after the rest have gone. It comes with a real caution, though: acetone will damage vehicle paint, plastics and rubber, and it soaks through some types of glove, so mix and apply it carefully. Among the cans, WD-40 is the surprise. Sold as a water displacer rather than a dedicated penetrant, it still took fourth, ahead of both PB Blaster and Aero Kroil.
Two things are worth carrying into a purchase. First, every treatment here beat an untreated stud, so the choice between cans matters far less than the choice to use one at all — and at $4 a can that is an easy decision to make. Second, a torch still beat all of them: the two studs held back for heat came apart more easily than any of the treated ones, so where heat is safe to use and there is time to apply it, that remains the strongest option on a badly seized fastener. Reputation is the thing to hold loosely here — Aero Kroil is the most expensive and most talked-about product in the group, and on these studs it finished behind a can costing less than a third as much.