If one used oil to fry meat and the next day used the same oil to fry something pareve (eg. french fries), is the pareve food considered 'meat'? Is there any differences between Sefardic and Ashkenazic Jews in this regard?
http://www.star-k.org/kashrus/kk-kosher-cons-handbk.htm (footnote 10):
One must also wait six hours if he ate french fries that were fried in oil previously used to fry chicken. Therefore, if one eats french fries (or other deep fried items) prepared in a fleishig restaurant, he should assume that he is fleishig unless the certifying agency of the restaurant indicates otherwise. Similarly, if one is fleishig one may not eat french fries that were fried in oil that was previously used to fry dairy products. When in doubt, consult with the restaurant’s certifying agency.