Throughout an oil's life cycle, its additives change – and the additives' structure correlates with their effect. Oil analyses can offer conclusions about the operational readiness of these active ingredients. Anti-wear (AW) and extreme pressure (EP) additives are particularly interesting, as they have to protect the lubricated components of the respective application within the tolerated limits. These additives are typically based on compounds containing phosphorus, which change over the oil's life cycle.

In the first instance, this concerns the additive content, which is traditionally determined in a lab using ICP-OES (inductively coupled plasma atomic emission spectroscopy). With the new phosphorus NMR, we can now also monitor the molecules of these phosphorus-based active ingredients in detail and identify any changes over an oil's service life. In particular, the phosphorus core is excited in a magnetic field and resonated via a radio frequency. These resonances depend on the molecule's structure and therefore provide what is known as a specific 'chemical shift'. 

The assessment of the results always requires a comparison with the corresponding clean oil. This is then analysed and its additive components containing phosphorus are determined using the phosphorus NMR. The used oil samples are compared to the reference to determine any percentage decrease in the active phosphorus-containing AW and EP additives. 
The phosphorus NMR therefore provides valuable additional information on traditional oil analyses. If any changes in the additive content are detected and the phosphorus NMR also shows significantly reduced – or even no – active AW or EP additives, that's a clear indication that the oil has been used to its capacity. In that case, the oil must generally be changed. However, the fall in the level of the active additive after an oil change is not, in itself, a reason to change the oil. Additives are designed to cover metal surfaces, which means it's normal for the additive content to drop after the oil has been changed. 

The additional NMR test is highly suited to large quantities of oil with long life cycles. The additional information provided on the condition of the additives offers greater certainty when deliberating whether the oil needs to be changed. Yet the new process also proves its worth in a range of other instances. Among other things, it can be used in damage assessments and development projects, such as testing engines. OELCHECK can then determine the fall in anti-wear additives with the phosphorus NMR alongside a traditional oil analysis.