[Auger1]

I've used a cutoff wheel to make a cut parallel to the cap to kind of break the threads loose. Just like cutting a nut loose the same way and taking the tension off the threads.

 

[Auger1]

Here's another tip my buddy told me about last weekend. When those oil cap drains get stuck he just heats the cap up with his propane torch and the cap just turns right off, easy-peasy.