The center's engineers visit and inspect each lab at least once a year. Larger facilities are checked more often. The center also maintains formal documentation of all reference test results. When the results come in from calibration tests, the data are converted into charts. If the variance is minor, another test is run.
Many inconsistencies are attributable to factors such as changes in test fuel or engine parts.
In extreme cases, the lab is shut down until the control tests return within limits. The TMC looks at the industry as a whole, at individual labs and at individual test stands within laboratories. We maintain a good sense of performance at all those levels. It enables us to spot, in a more timely manner, changes and problems that may be out there, and to take action. SAE defines the need for specific qualities in an engine lubricant, for example, the ability to work well in a more technically complex engine.