When using Plastigauge, what does it mean if the Plastigauge becomes wider?

When Plastigauge is used to measure oil clearance in an engine, the method involves placing a thin strand of the material between two surfaces, usually a bearing and a journal, then tightening the parts together to compress the Plastigauge. After removal, the width of the flattened Plastigauge can be compared to a calibrated scale.

If the Plastigauge becomes wider after being compressed, it indicates a larger oil clearance. The wider the Plastigauge spreads, the greater the distance between the surfaces, meaning that there is more space for oil to flow than intended. This is crucial for engine operation, as proper oil clearance ensures adequate lubrication while avoiding excessive wear and overheating. Larger clearances may lead to oil not being adequately retained in the bearing area, which can result in poor lubrication and increased wear on engine components. Thus, interpreting wider Plastigauge as indicating larger oil clearance is essential for maintaining engine performance and longevity.