Which Vehicle Underseal is the best?
On this webpage, I have included all the resources I have found on YouTube and other platforms that show useful tests of car, van, or motorhome rust underseal products. My favourite is Bilt Hamber Dynax UB, and the biggest shock was Lanoguard, which did not perform well. In fact, Lanoguard was beaten in two independent tests shown below by LPS3, Waxoyl by Jenolite, and Bilt Hamber.
This will help you make an informed decision about which rust inhibitors and underseal products are best for your vehicle. Next to each video, I will write a summary of the results to give you a quick snapshot.
This is one of the most-viewed underseal test videos on YouTube, with over 731,000 views, produced by the US-based channel Repair Geek. The presenter is a prominent advocate for Fluid Film and Blaster Surface Shield, both of which have sponsored his content at different times.
In this particular evaluation, LPS3 performs exceptionally well. As shown in a separate video below, LPS3 also won a comprehensive benchmark test of 33 different corrosion inhibitors conducted by the UK motorcycling channel Bennetts BikeSocial. However, please note that LPS3 is relatively expensive, difficult to source within the UK, and does not atomise cleanly through a standard underseal spray gun according to Repair Geek’s findings.
While Fluid Film provided solid structural protection against oxidation, it washed away very easily. It is important to note that the high-pressure jet wash experiment was conducted completely separate from the primary exposure test. In our own independent testing, the Fluid Film test piece succumbed to rapid rust formation shortly after being exposed to outdoor rainfall.
The next video features a comprehensive benchmark test of 33 corrosion inhibitors conducted by the UK motorcycling channel Bennetts BikeSocial, utilizing an accelerated salt spray test chamber. LPS3 secured first place, while Waxoil by Jenolite claimed a decisive second place, completely outperforming the competition.
In contrast, Fluid Film succumbed to rust very quickly. While Lanoguard outlasted most of the lower-tier products, it still began to corrode long before LPS3 and Waxoil. Please note that Bilt Hamber Dynax was not included in this video evaluation, nor was
This is my own independent testing—Jason from the Mobile Rust Doctor! As the largest and best-rated mobile rust undersealing service in the country, I wanted to put the top-performing products from the two videos above to the test, directly comparing popular US underseals against those widely used here in the UK.
For this benchmark, I evaluated Bilt Hamber Dynax UB and Dinitrol, both of which performed exceptionally well. In contrast, the Fluid Film test piece fared terribly. Lanoguard also corroded very quickly—showing rust within a matter of days—though it did not physically disintegrate the way Fluid Film did.
My primary observation was that Lanoguard washed away very easily, even during a second round of testing that included their thicker grease formulation. To be honest, I was not impressed with Lanoguard; it washed off quickly, rusted within days, and left a rather sticky, tacky residue on the surfaces where it did manage to stay.
Overall, Bilt Hamber Dynax performed brilliantly, matching the high standards of LPS3 and Waxoil by Jenolite. While Dinitrol achieved decent results, it behaves more like a paint, making it far more susceptible to chipping and cracking over time. Bilt Hamber, on the other hand, cures into a semi-hard wax layer. When I intentionally scraped the Bilt Hamber test piece, the film successfully self-healed, showing virtually no rust along the scrape line.
In the following comprehensive test including salt spray and a jet wash CRC 6026 and Flex seal came first and second out performing fluid film.
In this test from the USA/CANADA CRC again totally out performs fluid film. I could not buy CRC in the UK.