Treat your diesel right with Freedom Series 100% Synthetic Diesel Oil. Freedom Series emerged when AMSOIL and Fleece Performance Engineering partnered to develop an advanced formulation for diesel pickup trucks equipped with Fleece Performance products. Freedom Series Synthetic Diesel Oil provides excellent turbo cleanliness, superior soot control, and outstanding wear protection. The result: protection engineered to perform.
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Product data sheets
View, download, or save a copy of the Product Data Sheet or Safety Data Sheet for Freedom Series 15W-40 100% Synthetic Diesel Oil.
Freedom Series 15W-40 100% Synthetic Diesel Oil (FD1540) is the workhorse heavy-duty grade in the AMSOIL Freedom Series line, co-developed with Fleece Performance Engineering for late-model turbodiesel pickups that tow, haul, or run a horsepower tune. The 15W-40 grade is built from synthetic base oils with boosted detergent and dispersant chemistry to deliver turbo cleanliness, soot control, and ring-and-liner wear protection in API CK-4 (and prior) turbodiesel engines fitted with Fleece Performance products.
Outstanding wear protection for towing, hauling, and tuned trucks
Wear on rings and cylinder liners drives oil consumption up and pulls horsepower and fuel economy down. Freedom Series 15W-40 is formulated to deliver outstanding wear protection in demanding operating conditions, helping protect rings and cylinder liners so the engine maintains compression and minimizes oil consumption over long ownership. The result is reduced maintenance cost and downtime in pickups that work hard, including those modified for additional horsepower.
Turbo cleanliness for modified diesel pickups
Turbocharged diesels punish the oil at the bearing and ring belt, especially when the truck is pulling a heavy trailer or running an aggressive tune. Freedom Series 15W-40 is engineered to provide the turbo cleanliness needed to support reliability when towing, hauling, or modifying for additional horsepower. The Fleece Performance partnership shaped the formula around the duty cycle that modified turbodiesels see in real-world service.
Exceptional soot control and viscosity stability
Soot buildup in a diesel pickup can reduce power, increase abrasion, cause emissions-system problems, and decrease fuel economy. The synthetic base oils in Freedom Series are naturally resistant to oxidation and the thickening effects of soot contamination, while boosted detergent and dispersant additives keep soot particles suspended independently. That keeps small soot particles from agglomerating into the larger, wear-causing particles that grind on liners, lifters, and rings. Viscosity increase is minimized and soot-related wear is controlled. Freedom Series 15W-40 holds a high-temperature high-shear viscosity of 4.5 cP (ASTM D5481) and a total base number of 10.5 (ASTM D2896), so the oil retains its working viscosity and neutralizing capacity through high-temperature service.
Excels in extreme temperatures
Freedom Series 15W-40 effectively resists thermal breakdown for reliable performance in high-heat conditions. Unlike conventional 15W-40 diesel oils, the formula contains no wax and stays fluid in sub-zero temperatures for easier starting, improved oil flow, and reduced cold-start wear. The 15W-40 grade reaches a CCS viscosity of 5,272 cP at -20 C (ASTM D5293) and a pour point of -39 C (ASTM D97), with a viscosity index of 140 (ASTM D2270) so the oil holds its film across a wide operating temperature range.
Low-volatility formula reduces oil consumption
Freedom Series 15W-40 has a low rate of volatility, or burn-off, posting a NOACK volatility of 4.0 percent weight loss (ASTM D5800). Lower volatility reduces evaporative oil consumption during operation and passes less oil vapor into the combustion chamber, which supports emissions-system cleanliness and helps the formula retain its working viscosity after high-temperature service.
Recommended applications and service guidance
Use the live AMSOIL product page and your owner's manual to confirm the current viscosity, API category, OEM approvals, and service guidance for your engine before ordering. AMSOIL updates approvals and recommendations as formulas and manufacturer requirements change.
For extended service, follow the current AMSOIL guidance, your equipment manual, and oil-analysis results. Extended intervals are not appropriate for every engine or operating condition, especially modified engines, unusual fuels, racing use, or equipment with special service restrictions.
Typical technical properties
Property
Value
Kinematic Viscosity at 100 C, cSt (ASTM D445)
15.4
Kinematic Viscosity at 40 C, cSt (ASTM D445)
114.8
Viscosity Index (ASTM D2270)
140
CCS Viscosity, cP at -20 C (ASTM D5293)
5,272
Pour Point, C (ASTM D97)
-39
NOACK Volatility, percent weight loss (ASTM D5800)
Freedom Series 15W-40 100% Synthetic Diesel Oil is available in quart bottle (FD1540QT-EA) and case of 12 quarts (FD1540QT-CA). Using AMSOIL synthetic lubricants and practicing extended drain intervals does not void a new vehicle or equipment manufacturer warranty, and all AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty. Compare diesel grades and OEM categories with the AMSOIL Diesel Oil Guide, match the right product with the AMSOIL Vehicle Lookup Guide, then order Freedom Series 15W-40 100% Synthetic Diesel Oil.
Frequently asked questions
What is Freedom Series 15W-40 diesel oil designed for?
Freedom Series 15W-40 100% Synthetic Diesel Oil is the AMSOIL and Fleece Performance Engineering co-developed heavy-duty 15W-40 grade for turbodiesel pickup trucks equipped with Fleece Performance products. The application target is API CK-4 (and prior) turbodiesel pickups, including those modified for additional horsepower, that tow, haul, or run aggressive tunes.
How does Freedom Series 15W-40 compare to Signature Series Max-Duty 15W-40?
Both are 100 percent synthetic 15W-40 diesel oils sold under the AMSOIL brand. Signature Series Max-Duty 15W-40 (DME) is the broad heavy-duty workhorse with a long list of CK-4/SN, CJ-4, CI-4+, and OEM approvals for fleets, work pickups, and commercial equipment, available in package sizes up to 275 gallon totes. Freedom Series 15W-40 (FD1540) is the Fleece Performance co-developed pickup-truck formulation targeted at API CK-4 (and prior) turbodiesel pickups, especially those equipped with Fleece Performance products and modified for additional horsepower. The Signature Series Max-Duty 15W-40 guide entry in the AMSOIL Diesel Oil Guide covers the full comparison.
Is Freedom Series 15W-40 a CK-4 oil?
Yes. The application table covers turbodiesel engines specifying API CK-4 and prior heavy-duty diesel categories. Always confirm the API service category and any OEM approval required by the engine before changing oil, particularly for emissions-controlled engines that require a specific spec.
What is the drain interval for Freedom Series 15W-40?
For turbodiesel pickup service, Freedom Series 15W-40 is recommended for the drain intervals stated by the vehicle manufacturer. Refer to the owner manual for the specific oil change interval. Competition and racing service should be governed by the vehicle owner, who is responsible for determining the appropriate service interval when the truck is competing.
Can Freedom Series 15W-40 be mixed with conventional or other synthetic diesel oils?
Freedom Series 15W-40 is compatible with other conventional and synthetic engine oils, but mixing reduces the performance benefits of the formula. Aftermarket oil additives are not recommended for use with AMSOIL synthetic diesel oils.
Will running Freedom Series 15W-40 void a new diesel truck warranty?
No. Using AMSOIL synthetic lubricants and practicing extended drain intervals does not void a new vehicle or equipment manufacturer warranty, and all AMSOIL lubricants and filters are covered by the AMSOIL Limited Warranty.
Should this truck run a 15W-40, a 5W-40, or a 10W-30 Freedom Series oil instead?
The right grade depends on the engine manufacturer specification and the operating temperature range. Freedom Series Synthetic Diesel Oil is offered in 10W-30 (FD1030), 5W-40 (FD540), and 15W-40 (FD1540), with the 15W-40 grade positioned as the workhorse for warmer climates and heavy-duty pickup-truck duty cycles. Use the AMSOIL Diesel Oil Guide and the AMSOIL Vehicle Lookup Guide to confirm the correct grade for the engine.
