AMSOIL vs Delvac 1
Delvac 1 is ExxonMobil’s premium full-synthetic heavy-duty diesel line, and a legitimate product used across American and European fleets. Here’s how it holds up against AMSOIL Signature Series Max-Duty, backed by a real independent field study, not just marketing copy.
Alan Williams · AMSOIL Direct Jobber #1243776 · Tomball, TX · 225-441-6397
Independent Field Study, Real Trucks, Real Miles
The Nordic Waste Field Test: AMSOIL vs. Delvac 1 ESP
Nordic Waste, a refuse-hauling company based in Duluth, MN, ran a real-world field study comparing AMSOIL Synthetic 5W-40 diesel oil against four competitor oils, including Mobil Delvac 1 ESP, under genuinely severe duty conditions.
| Test Detail | Field Study Data |
|---|---|
| Test vehicle | 2006 International 7400 refuse hauler, hauling up to 22,000 lbs, up and down Duluth’s hills, roughly 12 hours a day |
| Sampling interval | Oil sampled every 50 to 75 hours, tested past 300 hours in service |
| Viscosity retention | AMSOIL was the only oil of the five tested to stay within its intended viscosity range through 371 hours (measured at 12.5 cSt) |
| Competitor result | All four competitor oils tested, including Delvac 1 ESP, sheared out of grade before 168 hours |
AMSOIL also showed stronger TBN (Total Base Number) retention throughout the test, meaning it held onto more of its acid-neutralizing reserve as the drain interval extended, a meaningful advantage for diesel engines, which generate more acid per combustion cycle than gasoline engines.
Running a fleet or a single diesel pickup? Tell me your engine and duty cycle, I’ll tell you the exact AMSOIL grade and interval, no upsell.
Official Manufacturer Specifications
Spec Sheet vs. Spec Sheet
Alongside the field study, here’s exactly what each manufacturer publishes on their own data sheets, for the specs the Nordic Waste test didn’t directly measure.
| Spec | AMSOIL Signature Series Max-Duty | Mobil Delvac 1 5W-40 |
|---|---|---|
| API Rating | CK-4 | CK-4 (per ExxonMobil PDS) |
| Rated drain interval | Up to 2x OEM (max 25,000 mi/1yr) | “Long drain capability,” no specific multiplier published for Delvac 1 itself* |
| Cold-flow rating | 5W-40 / 0W-40 available | Pumpable to -35°C (5W-40) |
| TBN | 12.5 | Not published on consumer-facing PDS |
| DPF/EGR/SCR compatible | Yes | Yes |
*Mobil’s own “2x average OEM drain interval” marketing claim applies specifically to Delvac Extreme, a different (lower) tier in Mobil’s diesel lineup, not the Delvac 1 product compared here. Worth knowing if you’ve seen that number attached to the Delvac name in general.
Get AMSOIL’s longer drain interval and field-tested protection at 25% off as a Preferred Customer.
What the Viscosity and TBN Results Mean
Viscosity shear is what happens when an oil’s molecular structure breaks down under mechanical stress, causing it to thin out and lose the film strength needed to protect engine components. In the Nordic Waste test, AMSOIL held its intended viscosity range through 371 hours, while Delvac 1 ESP and the other three competitors had already sheared out of grade by 168 hours, less than half that runtime.
TBN measures how much acid-neutralizing reserve the oil has left as combustion byproducts accumulate over the drain interval. Mobil doesn’t publish a consumer-facing TBN figure for Delvac 1 on its standard product page, so a direct spec-sheet TBN comparison isn’t possible from public data alone. But the Nordic Waste results give a real-world proxy: AMSOIL’s stronger TBN retention over the test period lines up with its longer viscosity stability. If TBN matters to your buying decision, ask your Mobil distributor directly for the figure, or request a batch-specific certificate of analysis.
Where Delvac 1 Is a Reasonable Choice
Delvac 1 is a real full-synthetic diesel oil, not a budget product. It’s a reasonable choice for:
- Mixed commercial fleets already standardized on Mobil products across multiple vehicle types
- Extreme cold-climate operations specifically needing the -35°C pumpability rating
- Operators with an existing ExxonMobil distributor relationship and volume account
Common Questions
Is Delvac 1 the same as regular Mobil Delvac?
No. Mobil’s diesel lineup has three tiers: Delvac 1 (premium full synthetic, compared here), Delvac 1300 Super, and Delvac Extreme. Each carries different specs and drain-interval claims. Check which one your current fill actually is before comparing marketing numbers.
Was Delvac 1 or Delvac 1 ESP tested in the Nordic Waste study?
The Nordic Waste field study tested Delvac 1 ESP specifically, an extended service formulation within the Delvac 1 family. The spec-sheet comparison above uses standard Delvac 1 5W-40 data, since that’s the product ExxonMobil publishes consumer-facing specs for.
Can I switch from Delvac 1 to AMSOIL without a flush?
Yes. AMSOIL is compatible with synthetic and conventional diesel oils. Drain at your normal interval and refill with the correct AMSOIL Max-Duty viscosity for your specific engine (see the full Diesel Truck Oil Guide for Cummins, Duramax, and Powerstroke specifics).
Does switching to AMSOIL 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 API specification and viscosity grade.
Get the Right Diesel Oil for Your Truck
Call and tell me your engine and model year, and I’ll tell you the exact AMSOIL grade, straight, no upsell.
More Comparisons & Guides
AMSOIL and Mobil Delvac are registered trademarks of their respective owners. Lube Oil Sales is an Authorized AMSOIL Independent Dealer (Dealer #1243776). This page contains affiliate links. Nordic Waste field study data as referenced elsewhere on this site’s Diesel Truck Oil Guide. Delvac 1 specifications sourced from ExxonMobil’s official product data sheets, current as of this publication. AMSOIL specifications sourced from AMSOIL’s official product data. Last updated: July 2026.