Candles vs. Olive Oil
Excerpt from Shabbos Secrets:
A husband came to the Sanzer Rav, the Divrei Chaim, to ask his advice about their domestic squabble. "My wife refuses to use olive oil for the Shabbos lights because her mother never used olive oil," the husband complained.
After hearing them out, the Divrei Chaim said, "Our Sages instituted the kindling of the Shabbos lights in order to promote domestic peace. How can Shabbos lights be a source of bickering to the point of causing the break-up of a marriage?"
Then he ruled, "The Sages placed the duty of kindling the Shabbos lights primarily on the wife. Therefore, the wife's custom should be followed, and she is not required to kindle using olive oil."