Can the validity of an oil sample change because the wear particles suspended in the oil deposit too quickly? One of our industrial gearboxes is regularly monitored using your lubricant analyses. The last analysis suddenly showed an exceptionally low PQ value. All other values were on trend. A control sample taken a few days later showed the expected PQ index. As always, we did not take the anomalous sample from or just in front of the oil sump after a long weekend. However, the gearbox was not in operation, otherwise we have always taken the sample during operation. Could this have influenced the result?