Red ATF (Dextron 3) is
a good penetrating oil. It'd highly detergent, won't hurt rubber seals, and if you use your electric heat gun, it will take 250 degrees OK.I mix the ATF with cheap paint thinner and keep it in an oil can. It's good for everything from pentrating oil to bike chains.Whatever penetrant you use, give it time and heat. A propane torch is OK if you wipe off the excess oil before you heat. Keep a bucket of water or a hose handy just in case. Put on more penetrant in small amounts when the metal is hot, with a Q tip or small brush. Try to loosen it when the metal is hot.If it doesn't come loose with the heat add more penetrant as the metal cools, let it sit over night, and repeat.Beware of spray cans on hot metal. Some of them use propane as a driver, so you could have a flame thrower.