Mercury - Oil Pressure Gauge 0-100 PSI Dual Scale Black Face 2-1/8" (52 mm) 79-8M0052848. Overview. The Mercury Oil Pressure Gauge (79-8M0052848) gives you a fast, accurate look at your engine's oil pressure so you can protect your motor and keep it running at its best. The dual-scale display shows readings in both PSI and Bar, making it easy to monitor in English or Metric units. It features a black face, bright white numerals, and a glass lens that stays clear in any light. Designed to fit a s