AMSOIL Signature Series Max-Duty 5W-40 Synthetic Diesel Oil
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The Most Popular Diesel Oil Viscosity
AMSOIL Signature Series Max-Duty 5W-40 is the most widely used viscosity in the Max-Duty diesel oil lineup. It delivers 6X more wear protection and is the go-to choice for Ford Power Stroke, GM Duramax, and Ram Cummins turbodiesel pickups.
Key Benefits
- 6X more wear protection than required by DD13 Scuffing Test
- Most popular diesel viscosity for modern turbodiesel pickups
- 76% less oil consumption than API CK-4 standard
- Extended drain intervals up to 3X OEM recommendation
- 60% better turbo cleanliness protection
- 2X better rust protection
Technical Specifications
| Property | Value |
|---|---|
| Kinematic Viscosity @ 100°C, cSt | 15.4 |
| Kinematic Viscosity @ 40°C, cSt | 94.5 |
| Viscosity Index | 173 |
| HTHS Viscosity, cP | 4.3 |
| Pour Point | -43°C (-45°F) |
| NOACK Volatility, % weight loss | 9.2% |
| Total Base Number (TBN) | 10.1 |
| Sulfated Ash Content | 0.99% |
Industry Certifications & OEM Approvals
API
- CK-4/SN
Cummins
- CES 20086, CES 20081
Detroit Diesel
- DFS 93K222, 93K218
Volvo
- VDS-4.5
Mack
- EOS-4.5
MB
- 228.31
Pros and Cons
Pros
- 6X more wear protection than required by DD13 Scuffing Test
- Most popular diesel viscosity for modern turbodiesel pickups
- 76% less oil consumption than API CK-4 standard
- Extended drain intervals up to 3X OEM recommendation
- 60% better turbo cleanliness protection
- 2X better rust protection
Cons
- Premium Investment: Higher initial cost compared to conventional or "shelf-brand" synthetic oils.
- Limited Local Retail: Primarily available through authorized dealers and specialized synthetic outlets. National Synthetics is a local stocking dealer. Call 1-678-944-8816 to confirm in-stock items for same-day local pickup.
Get AMSOIL Signature Series Max-Duty 5W-40 Synthetic Diesel Oil Today
Order directly through National Synthetics for Preferred Customer pricing and fast shipping.
SHOW MY PRICEIndependent AMSOIL Dealer #1858536
Shipping & Returns
Fast, Reliable Shipping
- Free standard ground shipping on orders of $100 ($130 in Canada) or more.
- Orders under the threshold ship for a flat $9.99 ($12.99 in Canada) freight charge.
- In-stock items typically delivered in two to three business days.
- U.S. and Canada only — no shipments to PO Boxes.
30-Day Return Policy
- Return unopened, currently marketed products within 30 days for a full refund (minus freight).
- Exchange unopened products within 90 days with no restocking fee.
- Special-order items are non-returnable.
- Returns are handled directly by AMSOIL.
Frequently Asked Questions
5W-40 is the most popular viscosity for modern turbodiesel pickups including Ford Power Stroke 6.7L, GM Duramax 6.6L, and Ram Cummins 6.7L. It's also widely used in medium and heavy-duty trucks. Check your owner's manual to confirm.
Customer Reviews
See all 1,508 reviewsGreat protection.
I use this for my 2025 Ram 2500 Cummins 6.7. It’s a great product for a reasonable price. I have my oil tested. I change my oil every 15,000 miles even though my test results say I can run it even longer.
Best diesel oil on the market
Run signature diesel 5w40 or 15w40 in everything we own from the grasshopper to tractors pickups and medium duty all on extended drains and some with amsoil bypass systems. Theres nothing out there that will run cleaner better or longer.
Diesel oil review
Couldn't be happier with the prompt arrival of my oil and filter and on the estimated time of arrival as well. My cummins is running like a clock with the 5w20 signature diesel oil only 1000 miles into the very first service with the filter and oil so I'm looking forward to the next 100,000 miles with it. I do want to add for your awareness that when it opened all three gallon oil jugs, each seal had popped open when I went to pour them in the pickup. I know that once it leaves your facility you have zero control over the "care" either UPS or FEDEX football teams provide the products. Be it elevation changes, being gallon jugs versus quart jugs applying more pressure inside if dropped or squished or what have you, I just wanted to pass it forward. Love the products thus far and look forward to continued use as well as use of some other products in the future
Good oil
Been good oil for me but it’s the 2nd time I’ve got the wrong filter that I ordered. I quit ordering for this reason because I live far out. Had to go buy a new filter again and now I this one that doesn’t fit.
Great but Pricing
I love their product that's highly recommended by Ram trucks but it costs ! Wish it was competitive with Rotella, Valvoline, and others.
Independent AMSOIL Dealer #1858536. Product information sourced from AMSOIL. Visit AMSOIL.com for the most current product details and availability.