Base stock interchange: A Balanced Approach is Key

Daphne Hunter, ExxonMobil

As global trade organizations licensed in more than 50 countries, the American Petroleum Institute (API) and the technical association of the European lubricants industry (ATIEL) are well respected by many in the finished lubricants industry. The two groups are responsible for monitoring global oil and gas trends and issuing standards and guidelines that are widely adopted around the world.

One particular set of guidelines that the groups manage is the development and maintenance of cost effective and technically robust interchange – or 'read-across' – guidelines for base stocks. Base stock interchange enables quick and efficient product development, which is important as industry specs become more complicated and the required tests become more expensive. However, in recent years, there has been a growing trend of individual automotive OEMs developing their own engine oil specs.

Consequently, this has added increased industry complexity as lubricant manufacturers work to meet new OEM requirements while also maintaining the more traditional API and ATIEL standards and certifications. Ultimately, given the global adoption across the industry, adhering to API and ATIEL standards and certifications as well as base oil interchange guidelines has become a required step in the formulation of quality finished lubricants. As the landscape continues to evolve, lubricant manufacturers need to take a thoughtful and balanced approach to meeting industry guidelines, while considering the guidelines, certifications, and standards necessary for specific OEM compliance, as well as their supplier’s capabilities.

Base stock interchange enables quick and efficient automotive engine oil product development

In the 1990s, as new base stocks were entering the market, API and ATIEL established definitions for base stock groups and classifications to help simplify the industry’s base oil selection and interchange process. This later helped inform the API’s formal engine oil licensing and certification systems, as well as ATIEL’s industry guidelines.  API and ATIEL established frameworks for interchanging base stocks produced by different manufacturers based on base stock classifications or groups.

Base stock interchange is considered by those qualifying engine lubricants against various industry and OEM standards an essential part of the process for minimizing cost and time. There are two types of base stock interchange: that which occurs within a base stock slate and that which occurs between base stock slates. Per API Publication 1509, a base stock slate is a product line of base stocks that have different viscosities but are in the same base stock grouping and produced by the same manufacturer. The concept of a base stock slate enables greater flexibility and faster qualification across many products, which ensures product integrity as it’s coming from the same source. Base stock interchange within a slate reduces development costs because it allows for the qualification of lubricants of various viscosity grades without needing to rerun a full engine test program.This type of interchange is termed “viscosity grade read across” or “VGRA.” Base stock interchange between different slates offers lubricant manufacturers significant blending benefits because it enables supply chain flexibility and is termed “BOI” or base oil interchange.

To meet evolving and ever-increasing performance and quality demands, automotive lubricant manufacturers are developing increasingly complex formulations based on OEM specs using a variety of base stock sources and additive components. Today, engine oils are frequently blended with base stocks from various manufacturers, and consequently, different slates.

Given the broad variety and quality of base stocks available in the current marketplace by multiple suppliers, it is imperative there is a clear, consistent testing framework in place to ensure the technical integrity and performance of the finished engine oil, regardless of any changes in the slate used or in the base stock manufacturer from whom base stocks are purchased. The frameworks set by API and ATIEL help ensure this marketplace consistency.

Interchange guidelines allow multiple base stocks to be approved with a specific additive system by reducing the number of engine tests needed to validate the use of alternative base stocks and viscosity grades when formulating engine oils that meet at least the minimum performance specifications. This can help lubricants reach OEMs and consumers more quickly because it not only avoids unnecessary and expensive engine testing programs, but also reduces new product development time.

Implementing base stock interchange

When it comes to implementing base stock interchange, it’s important to think about the strategies formulators use when developing a formulation to meet a specific industry or OEM specification. The formulator will conduct an engine test program to enable the broadest base stock interchange to reduce development costs and time. This enables quick turnaround when a lubricant manufacturer needs to utilize a new base stock in their finished lubricant.

With this in mind, a lubricant manufacturer selecting a base stock supplier should look beyond the price point and consider how the base stock fits within industry base stock interchange guidelines for the target lubricant specification.  Will the new base stock pass the current engine test or development program? If not, what is the development cost and time needed to qualify the new base stock? The ability to use base stock interchange guidelines is only one factor to consider when deciding on base stock suppliers. Other factors to consider include, but are not limited to, the base stock supplier’s supply chain security, access to products, and technical expertise.

OEMs push to go beyond API and ATIEL guidelines

In recent years, individual automotive OEMs have started developing their own engine oil specs in addition to those set by industry bodies inan effort to achieve better fuel economy and efficiency, while still providing exceptional engine protection. As today’s modern engines have become increasingly complex, some OEMs feel that current industry guidelines for base stock interchange between slates are too liberal. To maintain some control, OEMs have started creating specific standards that they believe are unique to their engines and specific interchange guidelines. These more individualized specs help guide lubricant manufacturers and additive companies as they develop products targeted specifically to those OEMs.

While adhering to specific OEM standards allows lubricant manufacturers to differentiate their products in the marketplace, it can also bring added formulation complexity and costs. It’s important to remember that while many lubricant formulations are compatible across a wide range of specs, OEM-specified engine oils may become mutually exclusive to each other.

Multiple engine oil specs: a balanced approach is key 

Base stock interchange enables quicker and more efficient product development. It is also beneficial to the base stock industry and necessary for practical category delivery timing and cost-efficient oil qualification. For the lubricant manufacturer and additive company, it reduces development costs since it significantly reduces the number of engine tests which need to be run to qualify a lubricant against a certain specification and can allow for the use of multiple base stock slates in the formulation of a lubricant.

As OEMs continue developing their own engine oil specifications, base stock manufacturers must take a balanced approach to producing engineered fluids that meet industry guidelines as well as individual OEM specs. Choosing a base stock supplier who understands your needs is more essential than ever. Suppliers with wide networks and strong technical expertise, as well as strong relationships with trade organizations and OEMs, will continue to be important in helping to navigate the increasing complexity of meeting changing industry and OEM specifications.

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About the Author

Global Product Development Advisor, Exxon Mobil Bastestocks & Specialties