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Synthetic Diesel Oil Frequently Asked Questions

amsoil diesel oil faqs

Frequently asked questions about AMSOIL Synthetic Diesel Oil From People Like You

I haven’t heard of AMSOIL

AMSOIL is not a mass-market brand. We are a brand for enthusiasts, with strong brand loyalty among millions of enthusiasts who are aware of the AMSOIL brand. Enthusiasts are passionate about their vehicles and are willing to pay a premium for high-performance products.

We make significant investments in the AMSOIL brand as the official oil sponsor of the Diesel Power Challenge and the Ultimate Callout Challenge, raising brand awareness with turbodiesel pickup enthusiasts.

Why should I use AMSOIL instead of my current major brand (such as Shell Rotella or Mobil Delvac)?

Shell and Mobil are well-respected brands that make good products; however, AMSOIL builds more protection into its products that goes far beyond the industry and OEM specifications. Signature Series Max-Duty Synthetic Diesel Oil delivers up to 6X more wear protection than required by the Detroit Diesel DD13 scuffing test.

For over 40 years, our focus on protection has helped us earn the trust of serious enthusiasts and people who depend on diesel power to make a living.

Can I use AMSOIL synthetic diesel oil without voiding my vehicle’s warranty?

YES. Using AMSOIL synthetic diesel oil has no effect on vehicle warranties. A federal law in the United States called the Magnuson-Moss Act (1975) prevents original equipment manufacturers from putting conditions on vehicle warranties attached to any product or service identified by brand, trade or corporate name, unless the manufacturer provides that product or service free of charge.

The law in Canada states that an OEM cannot require a consumer to use its parts/oil under the threat of voiding the warranty. This practice is referred to as “tied selling” and is in direct violation of the Canadian Competition Act due to its anti-competitive nature.

The Consumer Protection Acts in each province are the Canadian equivalent to the Magnuson-Moss Warranty Act. The law varies by province.

This means consumers have the freedom to use aftermarket products of their choice without fear of losing the original limited or implied vehicle warranty. For additional information, visit, or contact the AMSOIL Technical Department at (715) 399-TECH (8324) or

Will extending oil drain intervals void my vehicle’s warranty?

No. Extending oil change intervals will not void new vehicle warranties. To affect the vehicle warranty, it must be determined that the lubricant was directly responsible for the failure; if the oil didn’t cause the problem, the warranty cannot be voided, regardless of brand or length of time in use. For additional information, visit, or contact the AMSOIL Technical Department at (715) 399-TECH (8324) or

Does AMSOIL offer diesel oils for equipment calling for the API CK-4 specification?

Are the AMSOIL CK-4 diesel oils OK to use in older diesel engines?

YES. Max-Duty 15W-40 Synthetic Diesel Oil , Max-Duty 5W-40 Synthetic Diesel Oil , Max-Duty 0W-40 Synthetic Diesel Oil , Max-Duty 5W-30 Synthetic Diesel Oil , Heavy-Duty 15W-40 Synthetic Diesel Oil , Heavy-Duty 5W-40 Synthetic Diesel Oil , and Heavy-Duty 10W-30 Synthetic Diesel Oil are formulated with lower sulfur content to be compatible with today's high-speed, four-stroke diesel engines with exhaust after-treatment systems, and they also exceed previous diesel oil specifications. They are suitable for use in older diesel engines calling for API CJ-4, CI-4 Plus, and CF oils.

What are "normal" and "severe" driving conditions?

Each vehicle manufacturer defines "normal" and "severe" driving conditions for its equipment; AMSOIL recommends owners check these definitions in their owner’s manual to determine the service condition in which they typically drive.

AMSOIL defines normal service as personal vehicles frequently traveling greater than 10 miles (16 km) at a time and not operating under severe service.

AMSOIL defines severe service for gasoline engines as turbo/supercharged engines, commercial or fleet vehicles, excessive idling, first-time use of AMSOIL synthetic motor oil in vehicles with over 100,000 miles without prior continuous use of AMSOIL synthetic motor oil, daily short-trip driving less than 10 miles (16 km), frequent towing, plowing, hauling or dusty-condition driving.

AMSOIL defines severe service for diesel engines as extensive engine idling, daily short-trip driving less than 10 miles (16km) or frequent dusty-condition driving.

See the AMSOIL Product Recommendation and Drain Interval Chart for additional information.

Do I have to use an AMSOIL Ea Oil Filter with AMSOIL synthetic motor oil?

No. You can use whichever brand of filter you choose and AMSOIL synthetic motor oils will still be guaranteed to protect your vehicle for the advertised period. However, you will need to change your oil filter according to the filter manufacturer’s recommendations and top off the oil.

I understand AMSOIL synthetic motor oil resists boiling off in high temperatures. Do I still need to check the oil level in my car between oil changes?

Yes. It is normal for vehicles to use some motor oil. AMSOIL recommends checking your oil level every time you fill your fuel tank.

Can diesel oil be safely used in gas engines?

It depends on the specifications the diesel oil carries and the recommendation of the original equipment manufacturer (OEM). The American Petroleum Institute (API) publishes its “C” category of specification for diesel oil (currently CJ-4) and its “S” category for gasoline motor oil (currently SN). It’s common for today’s diesel engine oils to carry both the API CJ-4 and SN specifications. Though they’re truly designed for diesel applications, they can be used in gasoline applications for those who want to use one oil in all applications. If the diesel oil carries both specs, feel assured the oil is safe to use in diesel and gas applications. If the diesel oil does not carry the “S” category, it is not recommended to use it in gasoline applications.

When should someone use diesel oil in their gas engine?

If your gasoline engine is heavily modified to put out more horsepower, using a diesel oil can be beneficial. It’s likely modified engines will need a higher viscosity to withstand the increased stress. You can turn to diesel engine oils for those needs or you might want to consider a racing oil , depending on your engine modifications and lubrication requirements.

Videos:  What every diesel owner should know

AMSOIL: How It Is Made
AMSOIL Information Series - Synthetic Oil Basics
AMSOIL Diesel Truck Build
Diesel Power Challenge
AMSOIL Commerical Account Interview - Foster Trucking
AMSOIL Information Series: AMSOIL Grease Comparison Testing

Performance Tests

AMSOIL Diesel Fleet Fuel Economy Study in Stop-and-Go City ConditionsDiesel Fleet Fuel EconomyStudy in Stop-and-Go Conditions
AMSOIL Premium API CJ-4 5W-40 Synthetic Diesel Oil (DEO) Shear StabilityAMSOIL Premium API CJ-45W-40 Synthetic Diesel OilShear Stability
AMSOIL increases fuel economy by 6.54 percent in short- to medium-haul diesel applicationsDiesel Fleet Fuel Economyshort- to medium-haul dieselincrease fuel economy by 6.54 percent
Complete list of AMSOIL Performance TestingAMSOIL Performance Studies



Reviewed by Brad: space

Void Gm warranty?

Hi, just wondering will the 5w30 desiel oil void GM s warranty donto the fact that it doesn't have dexos2 on the label?

Item Reviewed: AMSOIL Synthetic Diesel Oil FAQs
Discussion Url | Calgary, Alberta

Re: Void Gm warranty?

Hi Brad. Signature Series Max-Duty Synthetic CK-4 Diesel Oil 5W-30 (DHD) does contain the DEXOS 2 specification, but Synthetic Diesel Oil SAE 5W-30 (DP530) does meet GM dexosD, dexos2 specifications. Replied by Tech Admin

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