Selecting the correct flow meter gun depends heavily on the viscosity and chemical properties of the fluid. For low-viscosity fluids like gasoline or water, a turbine flow meter is often sufficient. However, for high-viscosity liquids such as engine oil, gear oil, or hydraulic fluids, you must prioritize oval gear technology to ensure high precision. Always verify that the wetted materials (e.g., aluminum alloy, stainless steel, or specialized plastics) are chemically compatible with the fluid to prevent corrosion and seal failure.