Protection Boosted to the Max

You’re not tooling around town in a short-box whose heaviest load was that one time you went too far at the local wholesale club – you’re in a diesel. It’s raw power and whether you’re impressing your buddies or towing the work trailer, you need every ft.-lb. of torque. Pushing your pickup to perform might be a natural side-effect of sitting in the driver’s seat, but it also puts a lot of stress on your engine. And let’s face it – they aren’t giving these things away. Your investment deserves a diesel oil that’s up to the challenge. Your investment deserves AMSOIL.

More Built-In Diesel Engine Protection

Excessive wear to diesel cylinder liners and rings leads to increased oil consumption and loss of compression, reducing horsepower and fuel economy.

Independent testing shows AMSOIL Signature Series Max-Duty Synthetic Diesel Oil provides 6X more wear protection than required by the standard*. In the same test, AMSOIL Heavy-Duty Synthetic Diesel Oil delivers 4X more protection against wear than required by Detroit Diesel’s standard*.

More Built-In Protection

Operating at up to 150,000 rpm in temperatures that exceed 1,000°F, a turbocharger on a stock engine can dish out a lot of punishment to your oil. If it’s not formulated to take the beating, the oil can break down, creating deposits and wear. For some, stock engines don’t provide enough power, but dropping a tune on your engine puts even more stress on both your turbo and your oil.

Top-Grade Protection Against Deposits

Deposits caused by high turbo temperatures can lead to a host of problems, the most critical of which is bearing failure. Hot exhaust gases spin the turbine and expose that bearing to extreme heat. Your oil has to be up to the task of effectively removing heat from the bearing while providing proper lubrication to keep it spinning at high rpm. When your oil breaks down, excessive deposits form on the bearing and shaft that lead to a downward spiral for the longevity and effectiveness of your turbo.

AMSOIL Heavy-Duty Synthetic Diesel Oil is built to withstand the punishment turbos dish out, protecting against deposit formation in extreme temperatures. AMSOIL Signature Series Max-Duty Synthetic Diesel Oil provides protection boosted to the max, delivering up to 60 percent better turbo cleanliness* and withstanding the extra demands you place on that turbo when pulling heavy loads or updating the tune for maximum horsepower.

We deliver nothing but premium synthetic lubricants designed to help you get the most out of your turbocharged diesel engine.


Since December 1, 2016 the new American Petroleum Institute (API) has passed two diesel oil specifications, replacing the current API CJ-4 specification.

  • API CK-4 (improved performance for current model-year and older engines)
  • API FA-4 (improved performance for model-year 2017 and newer engines only)

Why is this change taking place?

There have been federal mandates to increase fuel economy while reducing emissions. To comply with this, manufacturers are designing engines that are tougher on oil. Modern diesel vehicles produce more horsepower and torque than ever, run much hotter, operate under higher pressures and have the ability to burn up to 20 percent biodiesel.

In order to keep up with these sophisticated new engines new diesel-oil technology is needed. Compared to the diesel engine oil you’re now using, diesel oils that meet the CK-4 or FA-4 performance specifications will deliver improved protection against wear and extreme heat.

CK-4 oils offer improved protection for both current and older engines. They are backward-compatible with the API CJ-4 diesel oil you’re likely now using. 

FA-4 oils, however, are different; they are not backward compatible with API CJ-4 oils. Instead, they’re designed to help increase fuel economy and reduce emissions in model-year 2017 and newer diesel engines (when called for in the owner’s manual). 

How does it affect me?

If you’re currently using an API CJ-4 diesel oil, simply begin using an API CK-4 oil of the correct viscosity.

If you own a 2017 model-year diesel, however, the manufacturer may recommend either a CK-4 or FA-4 oil it’s up to you which to use.

The new CK-4 and FA-4 formulations allow diesel owners to reduce their maintenance costs and extend the life of their equipment, allowing them to compete profitably in markets that demand peak reliability and efficiency.

AMSOIL has earned the trust of diesel equipment owners and has formulated new synthetic diesel oils that meet their demands and the demands presented by the latest diesel technology.

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