Does vegetable oil expand when frozen?

Very few substances do - they are characterized by the formation of open (usually tetrahedral) lattices as a solid. Water is the best known, along with the elements silicon, antimony, bismuth and gallium.

"Vegetable oil" is a wide-open term, which could refer to a mixture of various oils, or to a category of substances from individual vegetables - sunflower oil, safflower oil, etc. Even the single-vegetable oils are not pure substances, and unlikely to meet the requirements for expansion - I can find no evidence of any that do!

https://www.abc.net.au/science/articles/2012/10/15/3610808.htm

Most vegetable oil will freeze below 10F and will not expand, olive oil shrinks as it becomes more dense.

https://www.reviewho.com/will-vegetable-oil-freeze/ (satguru, moderator)