Making a red velvet cake. Recipe calls for 2 cups canola oil. Made this cake over the weekend and didn't have enough canola oil used veg oil

You could also try some other relatively neutral oil, like grapeseed oil if you have it. Peanut might work but I'm not sure how strong 1/2 cup would be in the grand scheme of things. Plus peanut and chocolate kind of go together anyway!

Use some olive oil but overdose on the sugar

You can use melted butter for the remainder, but be sure that when you melt it, you let the water cook off. Butter is an emulsion of 80% fat, 18% water, and 2% milk solids. To get the 4 ounces you are lacking, melt 5 ounces of butter and let the water "sputter" away. Excess water in any batter gives gluten a chance to overdevelop and produce a tougher cake.

Safflower oil would work. Just wouldn't use olive oil