There are very bland, ultra-filtered olive oils on the market (called light olive oil), and perhaps you have one of those. If you have an olive oil that is toward the virgin end of the olive oil spectrum, however, you will probably find it too flavorful for a cake.

The good news, however, is that Canola oil is among the blandest vegetable oils on the market. You can certainly use Canola oil in your cake and it will provide the lubrication needed without adding a hint of flavor.

And actually, you do have vegetable oil on hand. Olive oil, cottonseed oil, safflower oil, walnut oil, corn oil, grapeseed oil, sesame oil, soybean oil, pumpkin seed oil, sunflower seed oil, almond oil, hazelnut oil, peanut oil, rapeseed oil and its descendant Canola oil, etc. are all edible vegetable oils, as they all come from plants. Most products that are sold as "vegetable oil" are actually soybean oil. You are not going to want to mix some vegetable oils in a cake batter – sesame and flavorful olive oils being the most obvious – but they are all still vegetable oils.