AMSOIL vs Liqui Moly
Liqui Moly is Germany’s best-known synthetic oil brand. Before picking a side, here’s what both companies actually publish on their technical data sheets, including the one spec where Liqui Moly’s number is genuinely stronger.
Alan Williams · AMSOIL Direct Jobber #1243776 · Tomball, TX · 225-441-6397
The Number Most Comparisons Skip
On HTHS Viscosity, Liqui Moly’s Published Number Is Actually Higher
High-temperature high-shear (HTHS) viscosity measures how well an oil holds its protective film under load and heat. Liqui Moly Top Tec 4200 5W-30 publishes an HTHS of 3.5 mPa·s or higher at 150°C. AMSOIL Signature Series 5W-30 publishes 3.11 mPa·s. On this one metric, Liqui Moly’s number is higher, and that’s exactly why many European manufacturer specs (VW 504 00/507 00, MB-Approval 229.31, BMW Longlife-04) require oils in that higher HTHS range. This isn’t a flaw in AMSOIL Signature Series. It’s formulated toward dexos1 Gen 2 and ILSAC GF-6, both of which call for lower HTHS oils partly for fuel economy reasons. The two products are built to different certification targets, so before assuming one number automatically means “better,” it helps to know which spec your vehicle actually requires.
| Metric | AMSOIL Signature Series | Liqui Moly Top Tec 4200 |
|---|---|---|
| HTHS viscosity at 150°C | 3.11 mPa·s | 3.5 mPa·s or higher |
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Official Manufacturer Specifications
Current Spec Sheet Comparison
| Spec | AMSOIL Signature Series 5W-30 | Liqui Moly Top Tec 4200 5W-30 |
|---|---|---|
| Base oil type | PAO (Group IV synthetic) | Synthetic technology (blended synthetic base stocks) |
| Total Base Number (TBN) | 10.1 mg KOH/g | 8.5 mg KOH/g |
| NOACK volatility | 6.7% | 9.5% |
| HTHS viscosity at 150°C | 3.11 mPa·s | 3.5 mPa·s or higher |
| Pour point | -58°F (-50°C) | -42°C (-44°F) |
| Key certifications | API SP, dexos1 Gen 2, ILSAC GF-6, ACEA A5/B5 | ACEA C3, API SQ, BMW Longlife-04, MB-Approval 229.31/229.51/229.52, VW 504 00/507 00, Porsche C30 |
| Published drain interval | Up to 25,000 mi, 700 hrs, or 1 yr (AMSOIL’s own guarantee) | Up to 30,000 to 50,000 km, but only where your vehicle manufacturer’s own program authorizes it |
Specifications pulled directly from AMSOIL’s and Liqui Moly’s published product data sheets. AMSOIL’s advantage on TBN and NOACK supports its unconditional long-drain guarantee. Liqui Moly’s higher HTHS reflects the European OEM specs it’s built to meet, not a shortcoming in the AMSOIL formulation.
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Where Liqui Moly Is a Reasonable Choice
Liqui Moly is a legitimate, well-documented full synthetic oil, not a marketing shell. It’s a reasonable choice for:
- European vehicles with a specific OEM oil approval number (VW, BMW, Mercedes-Benz, Porsche) that Liqui Moly’s certification list matches directly
- Drivers who want a higher HTHS oil for sustained high-load or high-heat driving where that spec is called for
- Owners enrolled in a manufacturer long-life service program that authorizes the extended 30,000 to 50,000 km interval for their specific vehicle
Common Questions
Is Liqui Moly’s extended drain interval guaranteed like AMSOIL’s?
No. AMSOIL’s 25,000-mile interval is AMSOIL’s own printed guarantee, regardless of vehicle. Liqui Moly’s longer intervals depend entirely on your specific vehicle manufacturer’s long-life service program authorizing it. Without that authorization, Top Tec 4200 follows your owner’s manual schedule.
Does a higher HTHS number mean Liqui Moly is better?
Not automatically. A higher HTHS supports film strength under high load, which is why some European OEM specs require it. But AMSOIL Signature Series is formulated to a different target, dexos1 Gen 2 and ILSAC GF-6, which call for a lower HTHS range. Match the spec to what your vehicle manufacturer actually requires.
Does switching between AMSOIL and Liqui Moly void my warranty?
No. Under the Magnuson-Moss Warranty Act, a manufacturer cannot void your warranty simply for using a different oil brand, provided it meets the required specification and viscosity grade for your vehicle.
Can I mix AMSOIL and Liqui Moly?
Both are compatible with other synthetic and conventional oils, so mixing won’t damage your engine. For best results, drain fully and refill with one product rather than topping off a mixed fill.
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AMSOIL and Liqui Moly are registered trademarks of their respective owners. Lube Oil Sales is an Authorized AMSOIL Independent Dealer (Dealer #1243776). This page contains affiliate links. Liqui Moly specifications sourced from Liqui Moly’s official product information sheets (liqui-moly.com). AMSOIL specifications sourced from AMSOIL’s official product data sheet. Last updated: July 2026.