In my occupation as a sheetmetal worker some of the work I done was ducting for industrial machines, lathes and mills all cnc now that turn out mainly automotive wheels and the biggest problem we had was sealing because of oil in the cutting fluid being used the only thing I ever found that worked on oil was Ultra Blue RTV (not Blue only Ultra blue) it has a formula that eats though oil and adheres to the base material (probably an enzymes like they use for oil spills) anyhow it's good to 500 degrees F I have used this 5 years with models without fail, we even used it where we couldn't clean the surface properly to disassemble we had to destroy the ducting as we could never get apart unlike any other RTV.
I hope that many will try Ultra Blue and see it's unique qualities. I'm probably the only one that has used this as most go for the high temp that has been used for many years. Not disagreeing just showing advances in techincial fields. So it's oil resistant and high heat plus it eats though oil.
Copied from Permatex website"ULTRA BLUE No Leak RTV Silicone Gasket Maker


Ultra silicones were developed to meet today?s technology changes. Sensor-safe, low odor, non-corrosive. Outstanding oil resistance and joint movement values. Eight times more flexible than cork/composite gaskets; three times more oil resistant than conventional silicones. Temper-ature range -75?F to 500?F intermittent; resists auto and shop fluids and vibration.

Steve Maxwell