The Complete Guide to AMSOIL Diesel Oil & Fuel Additives
Modern turbodiesel engines — Ford 6.7L Power Stroke, Ram 6.7L Cummins, GM 6.6L Duramax, plus over-the-road, ag, construction, and marine diesels — operate under conditions that destroy conventional oils. Cylinder pressures exceed 30,000 psi. Soot loading from EGR systems doubles or triples vs. pre-emissions diesels. Turbocharger temperatures climb past 1,500 °F. AMSOIL builds two complete tiers of synthetic CK-4 diesel oil engineered specifically for these conditions, plus a third conventional CK-4 option for cost-sensitive marine and equipment applications — and a complete diesel fuel additive program that keeps modern ULSD-burning injectors clean, protected, and gel-proof.
Signature Series Max-Duty — AMSOIL's Flagship Diesel Oil
Signature Series Max-Duty (product codes DEO for 5W-40, DME for 15W-40, DTM for 5W-30, DZF for 0W-40, DTT for 10W-30) is the diesel oil for owners who want maximum protection and the longest possible drain intervals. In the Cummins ISB engine wear test, Signature Max-Duty delivers 6X more wear protection than required by the API CK-4 standard. With oil analysis and a matched AMSOIL Ea heavy-duty oil filter, drain intervals up to 25,000 miles or 1 year are routinely supported in pickup-truck severe-service operation.
Heavy-Duty Synthetic Diesel Oil — Premium Synthetic at Fleet Pricing
Heavy-Duty Synthetic Diesel Oil (product codes ADO for 5W-40, ADP for 15W-40, ADN for 10W-30) delivers 4X better wear protection than required by the Detroit Diesel DD13 scuffing test. It meets every major OEM diesel specification — Cummins CES 20086, Ford WSS-M2C171-F1, Mack EOS-4.5, Volvo VDS-4.5, Caterpillar ECF-3 — at a price point that works for fleet buying. The right pick for owner-operators, hot-shot operators, regional fleets, and anyone who wants true 100% synthetic protection without the flagship Signature Series price.
Fleece × AMSOIL Freedom Series — Performance & Modified-Diesel Oil
The Fleece Performance Engineering × AMSOIL Freedom Series is a co-engineered diesel oil line built specifically for performance, hot-shot, and modified turbodiesels. Available in FD540 (5W-40), FD1030 (10W-30), FD1540 (15W-40), FD1550 (15W-50 racing), and FDBRK (SAE 30 break-in oil). Freedom Series carries the API CK-4 license like AMSOIL's other premium synthetic diesel oils, but the additive chemistry is tuned for the higher cylinder pressures, sustained EGT, and stiffer injection events of tuned and competition diesel pickups. The 15W-50 racing grade (FD1550) is the right pick for sled-pull, drag, and dyno applications that don't quite need DOMINATOR's competition-only chemistry. The break-in oil (FDBRK) is friction-modifier-free for proper ring seating on freshly built diesel engines — the right first-fill for any Cummins, Power Stroke, or Duramax rebuild.
Commercial-Grade Diesel Oil — Fleet Bulk Pricing
For high-volume fleet, ag, and construction buyers, Commercial-Grade Diesel Oil (product codes SBD for 15W-40, SBDT for 10W-30) delivers API CK-4 protection at AMSOIL's lowest diesel oil price point. Sold in 1-gallon, 2.5-gallon, 30-gallon kegs, totes, and drums — sized and priced for fleets that consume multiple cases or drums per month. Commercial-Grade is the right pick when fleet accounting needs the lowest cost-per-quart on a CK-4 oil that still carries the AMSOIL name, the AMSOIL warranty, and the same major-OEM CK-4 approvals as the Heavy-Duty line. Pair Commercial-Grade with an AMSOIL Commercial Account for fleet-direct pricing and net-30 terms.
15W-40 Heavy-Duty Diesel & Marine Oil — Cost-Sensitive Equipment
15W-40 Heavy-Duty Diesel & Marine Oil (product code AME) is AMSOIL's conventional-base CK-4 diesel oil for marine diesels, gen-sets, off-road equipment, and applications where the OEM spec is met by conventional CK-4 and the budget calls for it. Same major-OEM approvals as the synthetic Heavy-Duty line — at the lowest AMSOIL diesel oil price point.
DOMINATOR® 20W-50 Competition Diesel Oil — Sled-Pull, Dyno, Drag
DOMINATOR® Competition Diesel Oil (product code DCO) is a purpose-built 20W-50 100% synthetic competition diesel oil for sled-pull, drag, dyno, and modified-diesel race applications. Maximum film strength and shear stability under sustained extreme-load operation — the heaviest competition diesel viscosity AMSOIL builds, and the right pick when peak film strength under cylinder pressure matters more than emissions compliance or drain interval. Boosted zinc additive chemistry for maximum scuff and wear protection in race-only diesels. Competition use only — not formulated for emissions-equipped on-highway diesel pickups. For tuned street and hot-shot diesels that still see DPF/DEF duty, choose Fleece Freedom Series 15W-50 Racing (FD1550) instead.
Diesel All-In-One — The Year-Round Daily-Driver Additive
Modern ULSD has reduced lubricity (sulfur removal at the refinery also strips the natural lubricity diesel injectors depend on), inconsistent cetane, and gels in cold weather. AMSOIL Diesel All-In-One (product code ADB) handles four jobs in one bottle — it cleans injectors and combustion chambers, restores lubricity to ULSD, boosts cetane for cleaner burn and faster starts, and disperses water that condenses in the fuel tank. Use it at every fill or every 4,000 miles for a daily-driver diesel pickup.
Diesel Cold Flow & Diesel Recovery — Winter Insurance
Below about 15 °F, #2 ULSD wax crystals start to drop out and clog fuel filters. Below 0 °F, gelling stops the engine cold. AMSOIL Diesel Cold Flow (product code ADD) is the preventive — added at every winter fill, it lowers the cold filter plugging point (CFPP) up to 35 °F, prevents wax crystal formation, and disperses water. AMSOIL Diesel Recovery (product code DRC) is the emergency rescue — it reliquefies already-gelled fuel, thaws iced fuel filters, and gets a frozen diesel started without towing it indoors. Carry a bottle of DRC in every cold-climate diesel through winter.
Diesel Injector Clean & Cetane Boost — Periodic Tune-Ups
For periodic deeper cleaning of fuel injectors and combustion chambers, AMSOIL Diesel Injector Clean (ADF) is the concentrated injector cleaner — restores horsepower and fuel economy, removes deposits, and helps minimize regeneration cycles in DPF-equipped trucks. AMSOIL Diesel Cetane Boost (ACB) is the standalone cetane improver — raises cetane up to 8 numbers for faster cold starts, smoother idle, more power, and reduced black smoke.
Compatibility with DPF, DEF, and Modern Diesel Emissions Systems
All AMSOIL CK-4 diesel oils — Signature Series Max-Duty, Heavy-Duty Synthetic, and 15W-40 Diesel & Marine — are low-SAPS, low-ash formulations engineered for full compatibility with diesel particulate filters (DPF), diesel oxidation catalysts (DOC), selective catalytic reduction (SCR), and diesel exhaust fluid (DEF) systems on every modern emissions-compliant diesel engine. Using AMSOIL CK-4 diesel oil will not damage your DPF or DEF system and meets the OEM warranty oil requirements.
Buying AMSOIL Diesel Oil in Florida and Across the U.S.
As an Independent AMSOIL Dealer based in Dade City, Florida, 1stsynthetic.com ships the full AMSOIL diesel lineup factory-direct anywhere in the United States. Tampa Bay diesel pickup owners running Sig Max-Duty 5W-40 (DEO) in their Power Stroke and Cummins trucks, central Florida fleet operators standardizing on Heavy-Duty 15W-40 (ADP) for their service trucks and equipment, hot-shot operators and owner-operators across the U.S. running Sig Max-Duty between 25,000-mile drain intervals — all order through 1stsynthetic.com to support an Independent Dealer while getting factory-direct AMSOIL pricing. Become a Preferred Customer to save 25% off retail on every diesel oil and additive order.
