If I mix olive oil and water and flour, will that make Matza Ashira I cannot eat during Pesach?
Matzah that was kneaded only with fruit juice such as wine or oil without any water is called Matzah Ashira (rich Matzah) that according to the opinion of the Shulchan Aruch does not become Chametz even if it sits all day. Therefore, it is permitted to be eaten on Pesach, but one cannot fulfill his obligation of eating Matzah with it, because it is not Lechem Oni (poor bread) and this is the Sephardic custom. According to the Rema and so is the Ashkenazic custom, Matzah Ashirah is not baked or eaten unless in extenuating circumstances for an ill or elderly person who needs it. Even then one should bake the dough immediately and not let it sit, because Lechatchilah (at the outset) we take into consideration the opinions of the Poskim that also fruit juice becomes Chametz and even quicker then water, and we also are concerned that maybe some water got mixed in the juice and then all agree it can become Chametz. In your case that you are using fruit juice with water, all agree it should not be done Lechatchilah, because it becomes Chametz quicker then other dough. Bedieved (post factum) if one kneaded with them, it should be baked immediately without letting it sit at all. And then it will be permitted for Sephardim to eat it like Matzah Ashirah. Because a Matzah is considered Matzah Ashirah even if the fruit juice is less than the water, as long as one can feel its taste. The Mishnah Berurah notes that also in extenuating circumstances where Ashkenazim are lenient and bake Matzah Ashirah for an ill or elderly person who needs it, one should not knead with fruit juice with water. [שולחן ערוך ורמ"א או"ח סימן תסב סעיפים א, ב, ד ובמ"ב שם].