Here's a few tips on how to ensure your mayo doesn't fail. First, make sure you use light olive oil, not extra-virgin. EVOO is way too heavy.) You can also use a high-oleic safflower sunflower oil, and my personal favorite grape seed oil. The seeds used to make these oils contain more healthy monounsaturated fats and less polyunsaturated fats, almost identical to olive oil. The flavor of all four of these oils is very mild, so they're ideal for making mayo. I've experimented with other oils, and find people don't care for the taste of other oils like walnut, avocado etc.