Motor Oil Classifications

Lube Notes - Motor Oil

Five Motor OilsThe ‘Old School’ axiom: “Oil is Oil” is simply wrong! Today’s engine oils, and all modern lubricants, are drastically improved in every aspect.

maxxTORQUE is dedicated to providing you with resource information to enhance your knowledge in all aspects for maintaining your truck. As a Certified Lubrication Specialist (CLS) with over 20 years of experience, I have continued to write a regular column, entitled, Lube Notes. The scope of Lube Notes has and will encompass lubrication, filtration, fuel additives, hydraulics, engine coolant / antifreeze, and various special subjects such as exhaust systems and DPF regeneration.


Everyone is always trying to tell you how you should maintain your vehicles and I realize that I’m just another, so-called professional, asking you to use precious time to consider what I have to say. I commit to you, that I will make it worth your time to read this column. I will bring you useful information so you can make educated decisions on how to service your vehicle. Maintaining a vehicle is about making decisions every day and having the information to make the right decisions is critical to being successful.

Proper service, including lubrication, may be the most important task that you, the owner, can take responsibility for to insure reliable trouble free operation of your vehicle. Millions, no Billions, of dollars are spent annually on service and lubrication for vehicles. Proper performance and meeting or exceeding rated life span are critical factors when determining overall life cycle cost. Trucks need to be on the road pulling trailers and working hard, not in the shop being repaired; trucks aren’t useful when they are out of service.

Enough about me, it’s time to get to the subject of this column, Lubrication. Let’s begin with understanding how to purchase the correct oil for your trucks.

Original Equipment Manufacturers (OEMs) such as, Ford, GM, Chrysler, Ram, Toyota, and Navistar determine the performance specifications for all lubricants for their equipment. These requirements are the basis of the certification parameters established by the American Petroleum Institute (API) to meet the API Classification. The API uses an alpha-numeric label that is displayed on the oil container with the latest classification being CJ-4 for diesel oils and SN for gasoline oils.

Additionally, the OEMs stipulate the required viscosity (sometimes referred to as weight) to use in every equipment application. Oil containers are labeled with the measured viscosity according to the Society of Automotive Engineers (SAE) system.

Figure 1, shows the actual label on two quart bottles of oil; one for diesel CJ-4 and one for gasoline SN. The containers are required to be labeled to clearly identify the API classification and the SAE viscosity.

API classifications are designed to be ‘backward compatible’, which requires that the latest classification will satisfy earlier classifications. For example, the current CJ-4 diesel oils are required to meet the specifications for the previous classifications, such as CH-4 and CI-4+. This is also true for gasoline oils where SN is the latest API classification and the SN covers all preceding classifications, such as SL and SM.

The first place to look for all service requirements, including lubrication, for your equipment is the ‘Operators Manual’ provided by the manufacturer. Great care is taken to insure the correct lubricants are specified for your equipment by the OEM. Remember, the OEM’s establish the required performance criteria that are the basis of the oil classifications established by the API. So it only makes sense that the OEM’s are the best source of the correct lubrication requirements for the equipment they manufacture. This is also true for viscosity requirements including adjustments for climate and expected temperatures. There are acceptable reasons to vary from the suggested viscosity but you should only make those variances with the advice of a professional. In subsequent articles, I will address the classification and ratings of transmission fluids and gear oils, both having their own peculiarities.

In addition to the API classification system, most OEM’s establish their own performance specifications for oil and lubricants. Usually, the OEM specification simply requires the oils to meet the API classification. In some cases the OEM will require additional criteria and the API classification is insufficient to meet the requirements. Recently, specifications requiring synthetic oils have become more frequent, especially in gear oils and transmission fluids. Again, this information will be in your ‘Operators Manual’ and it is important to be in compliance with these more stringent OEM specifications. Where these OEM specifications are noted it is imperative that you establish that the oil you are going to use meets these additional requirements. If your truck is under warranty and incorrect oil is used, it will void the warranty. Additionally, using the wrong oil can shorten component life and potentially cause damage to your equipment.

The ‘Old School’ axiom: “Oil is Oil” is simply wrong! Today’s engine oils, and all modern lubricants, are drastically improved in every aspect. The demands of modern equipment on lubricants requires that lubricant manufacturers employ only the most innovative technologies to insure successful lubrication. In the coming issues of maxxTorque, I will provide information and insights to help you, the end user, obtain the correct products for the specific applications.

Questions and/or comments, contact me.


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