I have a ceramic oil bottle that I don't use. It's just not as convenient as I hoped it would be. I'd like to donate it, but it still has an oil residue inside it. It has a long curved neck so sticking a bottle brush inside it isn't an option. Is there a way to get the oil out or are my only options throwing it out or donating it with the oil residue?
You can pour water and detergent inside, let it sit that way for a day to soften, then clean it by shaking the detergent solution vigorously and then filling it with water and emptying until the water comes out non-soapy. This should work, unless you let it sit for a long time empty, but with the residue of polyunsaturated oils inside. In that case, they can have gummed up.
If the brush problem comes because a straight brush can be stuck inside, but can't reach the nooks and the bottom, you could use a curved brush. These are sold to homebrewers in large sizes, I don't know if they are available for single bottles too.
Use automatic dishwasher detergent, very hot water, let soak overnight, shake, empty and rinse with very hot water, upend on a skewer to drain dry.