The model OVZ flowmeter is suitable for viscous oils, ranging from hydraulic to light gear oils, eliminating any problems associated with changes in viscosity during operation. It also provides the advantage of positive displacement technology at a rotameter price. This flowmeter has a cost-effective design allowing for stress-free maintenance. The only wearable components are the oval gears and their axles, allowing the two-step rebuilding process to be easily accomplished in minutes with no necessary recalibration. - See more at: http://koboldusa.com/news/product-news/oval-gear-flowmeter-oils-model-ovz#sthash.QUbScpEi.dpuf