These days, anything you buy seems to have an expiration date. You’ll find a “Best if Used By” label on everything from milk to batteries, but you won’t find such a date on greases and oils.

What is the acceptable storage life for a pail of Lithium Complex EP grease, or a drum of R&O 32 Turbine Oil? What difference does the storage environment make? What should you do to guard against storing a lubricant beyond its usable date? What tests should be conducted before using a lubricant that has been stored too long? The answers to these questions are important to achieving lubrication excellence.

The editorial staff of Machinery Lubrication magazine polled several lubricant suppliers, large and small, to see what they had to say about the issue of lubricant storage life limits, then reviewed the literature on the subject in efforts to report a consensus best practice. We found that the stored lubricants degrade for a number of reasons, which are summarized in Table 1.

Oxidation occurs in all oils that are in contact with air, including stored lubricants. The base oil and additive combination affects the rate of oxidation, and the presence of the thickener in grease can increase the degradation rate. But the environmental and storage conditions have the greatest influence on the rate at which the lubricant degrades. Increasing the temperature at which the lubricant is stored by 10°C (18°F) doubles the oxidation rate, which cuts the usable life of the oil in half. The presence of water, usually introduced as a result of temperature variations, increases the rate of oxidation.

Frequent agitation of the lubricant incorporates air into the oil. This increases the surface area contact between air and the oil, increasing the rate of oxidation. Agitation also serves to emulsify water into the oil, increasing its catalytic effect on the oxidation process. The storage container itself can affect the rate of oxidation. A poorly prepared steel drum can expose the oil to iron, which catalyzes the oxidation process. Of course, the use of nonreactive (plastic) containers or drum liners eliminates the metal catalyst affect on oxidation.

Lubrication book authors George Wills and Dr. A.R. Landsdown suggest that inventory levels be set so that lubricants are used within 3 to 12 months, depending upon the lubricant type (Table 2 below). Set inventory levels to stay within targets. If limits are reached, verify quality with oil analysis. Little is said with respect to influence of environment.

Product
Maximum Recommended
Storage Time
Lithium Greases
12 months
Calcium Complex Greases
6 months
Lubricating Oils
12 months
Emulsion Type
Fire-Resistant Fluids
6 months
Soluble Oils
6 months

Custom Blended Soluble Oils
3 months
Wax Emulsions
6 months
 
Table 2. Wills’ Recommended Shelf Life for Select Lubricants

The ML editorial staff polled several lubricant suppliers, ranging from large multi-national corporations to small independent suppliers, and lubrication consultants to get their recommendations for lubricant storage life. We asked them to recommend storage life limits for numerous lubricant types, ranging from simple R&O 32 turbine oil to EP grease, under varying temperature and humidity conditions. We were attempting to identify a consensus of opinion, or at least a reasonable range, to share with ML readers as a best practice. We found a startling variation in responses and a concerning degree of disagreement with recognized authors like George Wills and Dr. A.R. Landsdown. In a few cases, those polled were apprehensive to respond, probably because of the significant influence storage conditions have on storage life.

   As part of our research, we surveyed major oil companies, independent oil companies and a number of industry experts and end users to find out their recommendations on the storage life of lubricants. They were asked to provide their recommended length of time for storing certain oils and greases in various conditions. We questioned them about storing ten products, from Mineral R&O 32 to PAO-based EP polyurea grease; indoors at 68°F (20°C), outdoors in a warm climate at 85°F (30°C) and outdoors in a cool climate at 9°F (-13°C).

   Their responses varied. Some people provided information that was more helpful than others. Several gave ranges of recommended length of time, while others had little or no information to give.

   Recommended length of storage time, as collected from various sources surveyed, is condensed into the following tables:

Table 3 | Table 4 | Table 5 | Table 6

In the survey, we also asked end users about the guidance they had received from suppliers about lubricant storage life. The responses ranged from “pretty good guidance” to “no guidance whatsoever”. Some reported that their supplier gave them recommendations about the storage environment, but not about shelf life limits.

Because of the lack of consensus, we unfortunately cannot recommend a best practice to end users. However, the need to create one is evident. Industry needs guidance on the following issues that are critical to achieving lubrication excellence:

  • Appropriate environment for storing lubricants
  • Estimating quarterly, semiannual or annual usage requirements
  • Usage and storage methods (FIFO inventory system)
  • Storage life limits for various lubricants in various storage environments
  • Labeling requirements, including blending date, packaging date, delivery date and the date the lubricant was put into service by opening the containert Testing the condition of expired lubricants or those that have been compromised in storage

We propose that these questions be answered in the form of a standard (or series of standards) generated through the International Council for Machinery Lubrication (ICML). ICML is a nonprofit organization which is a voting member of the American National Standards Institute’s (ANSI) S2 Technical Advisory Group (TAG). If appropriate, the ICML standard can be advanced through ANSI as a candidate for adoption by ISO.

The foundation of effective lubrication, sometimes called “The Four Rights of Lubrication”, is right place, right time, right amount and right condition. Storage of new lubricants places a significant role in assuring that the oil is delivered in the right condition. Industry needs best practices and guidelines to follow. Despite the fact that our poll was not a controlled scientific study, the lack of consensus suggests that end users receive little guidance about lubricant storage and shelf life limits, and the information which is provided may be inconsistent.

Do you believe that lubricant storage and handling best practices should be formalized into a standard? Are you interested in becoming involved in the creation of an ICML standard for lubrication storage best practices? Please express your opinion and/or willingness to volunteer time and expertise to such an effort by e-mailing info@lubecouncil.org. Given an interest in the subject and a willingness to participate among individuals with the appropriate expertise, ICML will proceed to form an ad hoc committee to address the seemingly unresolved issue of lubricant storage and shelf life limitations.

When asked questions about storage of lubricants, three end users had different answers. Here is what they had to say:

Question: Have you received clear guidance from the oil company(s), concerning the suggested storage time/shelf life for oils or greases?

Answer # 1: Yes. We asked once, and the oil company supplied written guidelines. The document recommends protected storage: out of sun, rain, snow; away from extremes in heat and cold. To get the best performance, the document recommends inventory rotation. It also provides guidelines for determining age of the product - how to determine when it was manufactured.

Answer # 2: None; no information provided. Oil companies don’t readily give out information or guidelines of how or where to store lubricants properly. The user would have to pursue getting that information. If user specifically asked, the oil company could provide printed guidelines or offer training on best practices in storing lubricants.

Answer # 3: No. Oil companies don’t readily offer information on recommended storage length. Most of our oil is high-volume and does not sit around for too long before being moved out. We never really asked for guidelines, but I would think some guidelines are available in writing if requested. As far as other recommendations, oil companies do recommend storing drums on their sides and encourage vent filtration.