AMSOIL Signature Series 5W-40 Max-Duty Diesel Oil
100% synthetic diesel oil option with strong cold-start flow. Verify the required viscosity and specification for your exact engine before ordering.
View 5W-40 at AMSOILDiesel Engine Oil
AMSOIL Synthetic Diesel Engine Oil
Diesel engines combine high cylinder pressures, heat, soot and often long periods of towing, hauling or idling. AMSOIL offers synthetic diesel engine oils for light-duty turbo-diesel pickups, motorhomes, commercial trucks, agriculture and heavy-duty equipment.
Featured AMSOIL products
These products are relevant to this guide. Click a product to view current specifications and availability for the selected application.
AMSOIL Signature Series 15W-40 Max-Duty Diesel Oil
100% synthetic diesel oil option for severe-duty applications. Confirm your engine's required viscosity and specifications before ordering.
View 15W-40 at AMSOILProduct images courtesy of AMSOIL INC. Product availability and specifications can change; verify fitment before ordering.
Why AMSOIL is a strong choice for diesel engines
Diesel oil has to do more than lubricate bearings. It must manage soot, protect turbochargers, resist oxidation and maintain viscosity while the engine works under heavy load. That is exactly the kind of environment where a well-formulated synthetic lubricant makes sense.
AMSOIL offers diesel oils across several viscosity grades and performance levels so owners can match the lubricant to the engine specification and service. The goal is not to use the thickest or most expensive oil; it is to use the correct high-quality oil for the application.
Diesel Truck Guide
Engine oil, fuel additives, filtration and drivetrain maintenance.
Fuel Additives
Diesel injector cleanliness, lubricity, cetane and cold-weather products.
Filters
Oil, fuel, air and heavy-duty filtration options.
Gear Oil
Differentials, axles and gearboxes under load.
Built for heat, towing and long hours
Turbo-diesel pickups and motorhomes can spend hours under sustained load. Commercial engines may idle for long periods and then work hard. Synthetic base oils are valued because they are designed to resist heat-related breakdown and flow well during cold starts.
AMSOIL also offers complementary diesel fuel additives, filters, transmission fluids and gear oils, making it possible to approach the entire drivetrain as a system instead of treating engine oil as the only maintenance item.
Match the oil to the specification
Diesel engines may call for API CK-4, FA-4 or other specifications, and the required viscosity can vary by engine, climate and model year. Always use the vehicle/equipment lookup and confirm the product recommendation before ordering.
Common questions
What AMSOIL diesel oil should I use?
Use the AMSOIL lookup for the exact engine and confirm viscosity and required performance specifications.
Is synthetic diesel oil useful for towing?
Towing increases heat and load. A quality synthetic diesel oil is designed for demanding temperature and load conditions, provided it meets the engine requirements.
Does AMSOIL make products besides diesel oil?
Yes. AMSOIL also offers diesel fuel additives, filters, transmission fluids, gear lubricants, grease and other maintenance products.