AMSOIL vs Sea Foam
Both are well-known names for seasonal equipment storage. Here’s what real ASTM lab testing found when AMSOIL Gasoline Stabilizer and Sea Foam Motor Treatment were tested head to head on fuel stability and corrosion protection.
Alan Williams · AMSOIL Direct Jobber #1243776 · Tomball, TX · 225-441-6397
AMSOIL-Commissioned, Independent Lab Tested
What the ASTM Testing Actually Found
AMSOIL commissioned independent, third-party lab testing comparing AMSOIL Gasoline Stabilizer to Sea Foam Motor Treatment, with samples purchased and tested in 2022. As with any manufacturer-commissioned test, it’s worth knowing AMSOIL selected the tests and paid for the lab work, though the ASTM methods used are recognized industry-standard procedures, not something AMSOIL designed itself.
| Test (ASTM Method) | AMSOIL Gasoline Stabilizer | Sea Foam Motor Treatment |
|---|---|---|
| Gasoline oxidation stability, triple-length (D-525) | 4,320 minutes | 536 minutes |
| Corrosion protection, synthetic sea water (modified NACE TM0172 per D-665B) | Metal kept corrosion-free | Visible corrosion present |
4,320 minutes is 8 times longer than Sea Foam’s result in the same test. The corrosion test used a modified NACE TM0172 procedure with synthetic sea water, relevant to equipment exposed to marine or humid coastal environments, like outboard motors and personal watercraft.
Storing a boat, motorcycle, or seasonal equipment? Tell me what and for how long, I’ll confirm the right product, no upsell.
Official Manufacturer Specifications
Treat Rate and Application
| Spec | AMSOIL Gasoline Stabilizer | Sea Foam Motor Treatment |
|---|---|---|
| Treat rate | 0.4 oz per gallon of gasoline | 1 oz per gallon of gasoline |
| Claimed storage duration | Up to 12 months | Manufacturer recommends periodic use, not a fixed single-treatment duration |
| Also marketed for | Fuel storage stabilization specifically | Engine cleaning, injector/carburetor cleaning, and storage stabilization |
AMSOIL’s lower treat rate means one bottle covers considerably more fuel than an equivalent-sized bottle of Sea Foam at its recommended dose.
Get AMSOIL Gasoline Stabilizer at 25% off as a Preferred Customer.
Where Sea Foam Is a Reasonable Choice
Sea Foam has built its reputation on more than just storage stabilization. It’s a reasonable choice for:
- Active engine and injector/carburetor cleaning on a running vehicle, a use case AMSOIL Gasoline Stabilizer isn’t specifically marketed for
- Owners who want one product marketed for both cleaning and storage, rather than a product focused specifically on stabilization
- Anyone already happy with Sea Foam’s results and not dealing with long-term storage in a harsh or coastal environment
Common Questions
Is AMSOIL Gasoline Stabilizer the same thing as Sea Foam?
Not exactly. Sea Foam Motor Treatment is marketed for both active engine cleaning and storage stabilization. AMSOIL Gasoline Stabilizer is purpose-built specifically for fuel storage stability and corrosion protection, which is reflected in its ASTM test results above.
What equipment is AMSOIL Gasoline Stabilizer meant for?
Motorcycles, snowmobiles, ATVs, UTVs, outboard and stern-drive marine engines, personal watercraft, lawn equipment, chainsaws, snowblowers, generators, and cars and trucks, anything that might sit unused for weeks or months at a time.
Do I still need to drain the fuel before storing equipment?
No, that’s the point of using a stabilizer. Draining fuel can actually invite corrosion on bare metal inside the tank and cause gaskets and seals to dry out and crack. Treating the fuel in place and leaving the tank full is generally the better approach for most stored equipment.
Can I use both AMSOIL Gasoline Stabilizer and Sea Foam together?
It’s not necessary. Since AMSOIL Gasoline Stabilizer is specifically formulated for storage stability, using it alone for that purpose covers what Sea Foam would otherwise be doing in that role.
Get Your Equipment Ready for Storage
Call and tell me what you’re storing and for how long, and I’ll confirm the right product, straight, no upsell.
More Comparisons & Guides
AMSOIL and Sea Foam are registered trademarks of their respective owners. Lube Oil Sales is an Authorized AMSOIL Independent Dealer (Dealer #1243776). This page contains affiliate links. ASTM lab test data based on independent third-party testing of AMSOIL Gasoline Stabilizer and Sea Foam Motor Treatment samples obtained in 2022, as published by AMSOIL. AMSOIL and Sea Foam specifications sourced from each manufacturer’s official product data. Last updated: July 2026.