What is the first rule for collecting oil samples?

The first rule for collecting oil samples is to sample when the machine is running. This practice is essential because it ensures that the oil being sampled is representative of the operating conditions and the actual state of the lubricating fluid while the machinery is performing its intended function. Sampling during operation captures the oil's full characteristics, including any contaminants, wear particles, and degradation products that accumulate during normal operation. This firsthand insight is critical for accurately assessing machinery health and making informed maintenance decisions.

Sampling when the machine is not running or at ambient temperature would not provide a true reflection of the oil’s condition under load, leading to potentially misinformed evaluations of equipment health. Collecting a sample before replacing the filter might also yield misleading results, as newer oil can skew the analysis of contaminants and wear debris already present in the system.