Fluorosilicone (FVMQ) combines the good high- and low-temperature properties of silicone with limited fuel and oil resistance. Fluorosilicones provide a much wider operational temperature range than Fluorocarbon rubbers. Primary uses of fluorosilicone O-rings are in fuel systems at temperatures up to +177°C (+350°F) and in applications where the dry-heat resistance of silicone O-rings are required. Fluorosilicone O-rings may also be exposed to petroleum based oils and/or hydrocarbon fuels. Fluorosilicone o-rings are commonly used in aircraft fuel systems
In some fuels and oils; however, the high temperature limit in the fluid list is more conservative because fluid temperatures approaching 200°C (390°F) may degrade the fluid, producing acids which attack fluorosilicone O-rings. For low temperature applications, fluorosilicone O-rings seal at temperatures as low as -73°C (-100°F). Fluorosilicone o-rings are ideal in static applications, but have poor abrasion resistance due to physical characteristics.