Tow-rig oil that doesn’t quit at 25,000 miles.
For pickup and medium-duty tow rigs running a Power Stroke, Duramax, or Cummins across Central Washington — short hauls, long grades, and the cold-idle mornings in between. AMSOIL Signature Series Max-Duty Synthetic Diesel Oil 15W-40 is built for exactly that duty cycle, and every order runs through the dealer referral so Preferred Customer pricing applies at checkout.
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One line tuned for the tow-rig duty cycle.
Top-tier 100% synthetic, sized for the platforms most common in the region. Click through to amsoil.com — Preferred Customer pricing rides along on the dealer referral tag, so the price at checkout is the dealer rate.
15W-40 — Diesel
AMSOIL’s flagship 100% synthetic diesel engine oil — the top-tier Signature Series line, rated for the 25,000-mile / 1-year drain interval under normal operation. The 15W-40 viscosity is the factory fill for every common tow rig in the region (Ford 6.7L Power Stroke, GM 6.6L Duramax, Ram 6.7L Cummins) and carries the additive package that holds film strength under heat, soot, and load.
Best for: ¾- and 1-ton pickups, Power Stroke / Duramax / Cummins tow rigs, fleet diesels.
Shop on AMSOILBuilt for heat, soot, and load cycling — not commute duty.
Towing a trailer up a grade on I-90, then idling a cold block the next morning — that is the cycle that breaks conventional oil. The Signature Series full-synthetic formula is engineered for exactly that swing.
Film strength past 250 °F
Towing a load up a long grade pushes sump temperatures past 250 °F. Conventional blends thin out and lose film strength; the Signature Series synthetic base stock holds viscosity in that window so bearings and cam lobes stay separated when the oil is hottest.
EGR soot stays suspended
Modern diesels with EGR dump soot into the sump — a conventional oil thickens into sludge long before the drain. The Signature Series dispersancy suspender package keeps soot in suspension so it drains cleanly at the 25,000-mile interval instead of baking onto hot internals.
Handles the swing
The combined cycle — idling a 1-ton with a plow for an hour, then towing a loaded trailer home — is where conventional diesel oil gives up. Signature Series’ additive system is built for that swing: a cold start followed by sustained high load on the same fill, with no visible thinning and no diesel-fuel dilution in weekly used-oil reports.
Drain interval assumes normal operation under AMSOIL’s severe-service schedule with extended OCI monitoring — the dealer adapts the recommendation to your actual duty cycle on request.
Ready to enroll through the dealer referral?Pricing comes from AMSOIL — not added by the dealer.
Enroll in Preferred Customer