Class 8 Diesel Oil — Head-to-Head
Diesel Oil Comparisons for Semi Trucks
Every comparison on this site is written by a Red Seal 310T technician with 28 years on Class 8 equipment. No brand sponsorship bias. No marketing copy. Just what the data and the drain plug tell you.
These comparisons pit AMSOIL against the oils most commonly specified or stocked at truck stops and fleet accounts — Rotella T6, Mobil Delvac, Pennzoil, Petro-Canada, and Castrol. Each page covers wear protection data, spec approvals, drain interval capability, and which application each oil actually fits.
AMSOIL vs The Competition
The most-searched Class 8 comparison. Rotella T6 is the default fleet spec at thousands of accounts. Here's what the wear data actually shows.
Read Comparison →Delvac 1 is Mobil's full-synthetic flagship for heavy-duty diesel. How does it stack up against Signature Series on wear and extended drains?
Read Comparison →Delvac 1 ESP targets European specs and low-SAPS applications. Different product, different approvals — compared against the right AMSOIL tier.
Read Comparison →Delvac MX is Mobil's synthetic-blend entry point for heavy-duty diesel. Compared against AMSOIL's Heavy-Duty tier on protection and value.
Read Comparison →Pennzoil Ultra Platinum uses PurePlus gas-to-liquid base oil technology. Strong marketing — but how does it perform against a purpose-built diesel synthetic?
Read Comparison →Castrol Vecton is a common fleet spec in Canada and the UK. System Pro technology claims extended drain capability — tested against Signature Series.
Read Comparison →Duron-E is Petro-Canada's heavy-duty synthetic, widely used across Canadian fleets. Compared on spec approvals, wear data, and extended drain support.
Read Comparison →How These Comparisons Are Done
Every comparison follows the same four criteria. No test is invented here — the data comes from published ASTM test results, OEM spec sheets, and AMSOIL technical documentation.
Four-Ball Wear Test (ASTM D4172) scar diameter and the Detroit Diesel DD13 Scuffing Test for Specification DFS 93K222. Lower scar = more protection.
API classification, OEM approvals (Detroit DFS, Cummins CES, Mack EOS, Volvo VDS), and whether the oil carries the spec or just claims compatibility.
OEM-recommended interval vs. extended drain capability. Only full synthetics with documented long-drain additive chemistry qualify for extended intervals.
Which engines, duty cycles, and operating conditions each oil actually fits. A 15W-40 CK-4 and a 5W-30 FA-4 are not the same product — context matters.
Which AMSOIL Tier Is Being Compared?
AMSOIL makes three tiers of diesel oil for Class 8 applications. Each comparison specifies which tier is relevant — the 6× wear claim applies to Signature Series only.
| Product | Wear Protection | Drain Interval | Best For |
|---|---|---|---|
| Signature Series Max-DutyDME 15W-40 / DHD 5W-30 / DEO 5W-40 | 6× wear protection | Extended drain capable | Owner-operators, long-haul fleets maximizing uptime |
| Heavy-Duty SyntheticADP 15W-40 / ADO 5W-40 | 4× wear protection | OEM interval | Full synthetic protection at lower upfront cost |
| Commercial-GradeSBDF 15W-40 / SBDT 10W-30 | 2× wear protection | OEM interval only | Fleets upgrading from conventional oil |
Not Sure Which Oil Fits Your Engine?
Use the AMSOIL heavy-duty vehicle lookup to match oil to your specific engine, emissions tier, and OEM spec requirements.