Silicone Hoses are lined with Fluorosilicone rubber (FVMQ) or Fluoroelastomer (FKM) for resistance to oil and fuel and their mists, and certain chemicals in the Charge-Air-Cooler, SCR, or EGR systems.

Although Flurosilicone has a vast temperature range, from -55⁰C up to +230⁰C, it is sometimes inadvertently used at much higher temperatures.
In the below table, you can see the deterioration in physical properties, when we aged the grades of FVMQ and FKM that we regularly use at Shore Auto, for 72 hours at 260 degrees centigrade.