Ask the Expert

the Expert

Q:

Can you confirm that there are no greases with a NLGI consistency number with a “Grade N2” designation?

A:

We can confirm that there is no NLGI consistency grade designated N2. Please visit the NLGI website for a complete listing of all NLGI Certified greases with the consistency grade included.

Q:

We are trying to qualify a grease for an NLGI classification - what needs to happen get this done? We will be performing D217 Cone Penetration on their grease - would you accept our results to qualify the grease?

A:

The requirements for qualifying a grease against the NLGI GC or LB service categories are detailed in ASTM D4950. All tests listed must be performed to qualify a grease against either of the categories. A D217 Penetration test performed as prescribed in the test method is considered to be suitable to be part of the data used to qualify the grease.

Q:

My company has a standard grease we¹re currently using. But it is causing us some problems so we are looking at alternatives. I am trying to find a list of grease manufacturers that have a significant international presence. If I find the perfect grease in USA and it isn¹t available in China, Brazil, etc. it does me no good. Is that something your organization can help with?

A:

NLGI cannot recommend a grease manufacturer, as there are many that make up NLGI’s membership. However, there are many grease manufacturers with an Internet presence or that can be found in trade magazines, journals, and periodicals. Most multinational oil companies produce lubricants and greases and most of them have presence in major industrial markets such as the USA, Europe, Japan, China, Brazil, etc. Attending NLGI’s annual meeting is an opportunity to network with many grease manufactures.

Q:

Would you please advise me if greases in different consistency could be mixed? For example, could grease with NLGI 2 replace by grease with higher or lower NLGI, e.g. NLGI 1 or 3 and 4?

A:

Greases of different NLGI consistency grades can be mixed. The mixture typically has a consistency intermediate to the two products that were mixed. Generally, a product with a given consistency grade (i.e. 1, 2, 3, etc.) is specified by the equipment or bearing manufacturer for a given set of operating conditions (operating temperature, bearing type and size, speed, and load). That grease should be used in the application, and greases of different consistency generally should not be mixed with the specified grease. In some cases, grease consistency is changed with the seasons (i.e. NLGI 2 in summer and NLGI 1 or 0 in winter) in equipment that is exposed to outdoor temperatures. In places with a consistent year-round climate, such as Singapore, a single consistency grade product would be preferred. The above assumes that the two products being mixed are compatible, and mixing them would not result in incompatibility of the thickeners in the greases. Incompatibility often results in the mixture of greases becoming soft, even fluid, and not staying in the application. In some cases the mixture becomes stiffer, resulting in difficult poor performance in the application and relubrication. A mixture of greases becoming either fluid or extra stiff can result in poor lubrication and premature equipment failure. Mixing of greases should be investigated in the laboratory prior to mixing the greases in an application.