Why Alcohol-Based Filter Oil Damages Foam Filter Glue: The SDS Evidence
Short answer: we tell every customer not to use standard No-Toil oil or cleaner on a FunnelWeb filter, and for years the explanation was simply "it attacks the glue." We can now show you why, using No-Toil's own published Safety Data Sheet. The standard biodegradable oil (NT201/NT218, SDS revision 04/2025) lists 10–25% alcohol as an ingredient, and its physical constants match isopropyl alcohol. IPA is a polar solvent, and the adhesives that hold foam filters together are polar polymers. IPA is literally sold as a thinner and remover for the most common one. This is not a quality problem with anyone's oil. It is a chemistry incompatibility between an alcohol carrier and filter glue, and it is why the same filter that lives for seasons on petroleum oil can delaminate after a few cycles of an alcohol-based product.
What the SDS shows
Section 3 of the NT201/NT218 sheet lists two main components: a polymerised fatty acid at 50–75%, and "Alcohol, 10–25%, Proprietary," classified as a Category 2 flammable liquid with H319 and H336 hazard codes and a workplace exposure limit. Section 9 pins down which alcohol. Compare the listed constants with textbook isopropyl alcohol:
| Property | No-Toil SDS | Isopropyl alcohol |
|---|---|---|
| Boiling point | 180°F / 82.2°C | 82.6°C |
| Specific gravity | 0.789 | 0.786 |
| Vapor density | 2.07 | 2.07 |
| Vapor pressure | 33 mmHg | 33 mmHg at 20°C |
| Flash point | 68°F / 20°C | 12–20°C |
| Odor | "Slight alcohol" | Characteristic alcohol |
Every constant lines up. The fatty acid base itself is a heavy, non-volatile, tacky bio-oil and is not the issue. The issue is the carrier.
Why alcohol eats glue and petroleum oil does not
Like dissolves like. Foam filter bond lines are almost always one of two adhesives: polychloroprene (neoprene) contact cement or a polyurethane. Both are polar polymers. Isopropyl alcohol is a polar protic solvent, and it is the standard thinner and remover for contact cement; that is exactly the job it does in a workshop. Petroleum filter oil is the opposite case: non-polar and high molecular weight, with essentially zero solvency for those polymers. That is why decades of petroleum-oiled filters never showed this failure, and why Motocross Action's observation that "alcohol also eats the cheaper glue on some filters" matches what riders find in the airbox.
Why it gets worse in a sealed bag or a closed airbox
That 33 mmHg vapor pressure cuts both ways. The alcohol is volatile enough to wick into the bond line by capillary action while the oil is spreading through the foam. In open air it eventually flashes off. But if the freshly oiled filter goes into a zip-top bag, or straight into a closed airbox, before the alcohol has fully evaporated, it sits trapped in the glue joint and keeps working on it. The common habit of pre-oiling a filter and bagging it for later, a good habit with the right oil, becomes the worst case with an alcohol carrier.
This is also why one piece of advice applies to every filter oil, whatever the base: after oiling, give the filter about 30 minutes in open air before it goes into the airbox or a storage bag, so the carrier can flash off completely.
The cleaner doubles the attack
The matching cleaner (NT03) is a sodium-salt solution at pH 11.3–11.6. Strongly alkaline solutions hydrolyze the ester linkages in polyester-backbone polyurethane adhesives. So a full clean-then-oil cycle hits the bond line twice, with two different mechanisms: alkaline hydrolysis in the wash, then solvent attack in the oiling. A filter serviced this way is being taken apart a little on every cycle.
The notable exception in No-Toil's own lineup
No-Toil also sells an Evolution line (EV-101/EV-118). Its SDS lists a fatty acid blend plus a nonionic surfactant, no GHS hazard classification, non-flammable, boiling point above 212°F. In other words: the alcohol is gone, and with it the mechanism that attacks glue. Riders committed to the biodegradable route should use the alcohol-free version, never the standard one. The fact that an alcohol-free variant exists at all tells you the problem was real.
What this means for your FunnelWeb
- Never use standard No-Toil oil (NT201/NT218) or cleaner (NT03) on a FunnelWeb filter. Damage from alcohol-based products is identifiable and is not covered by warranty.
- Check any biodegradable oil's label or SDS for alcohol content before it touches your filter.
- Our recommendation is a petroleum-based oil, and specifically a grease-based one that cannot migrate: why FunnelWeb uses a grease-based filter oil covers it.
- Not sure what oil family fits your riding? Start with the filter oil types guide.
Frequently asked questions
My filter already delaminated. Was it the oil?
If the foam separated at a glued seam after cycles of an alcohol-based oil or a high-pH cleaner, that is the signature. Mechanical damage looks different: torn foam cells rather than a cleanly failed bond line.
Is this specific to FunnelWeb filters?
No. The adhesives involved are used across the foam filter industry, which is why the same complaint shows up on many brands. We publish the chemistry because we would rather explain a warning than replace a filter.
What should I clean with instead?
A dedicated foam filter cleaner or mild soap and warm water, then dry fully and re-oil. Full walkthrough: how to clean and re-oil a foam air filter.
Sources: No-Toil SDS for NT201/NT218 (revision 04/2025) and NT03; No-Toil Evolution EV-101/EV-118 SDS; published physical properties of isopropyl alcohol; Motocross Action Magazine.