In a blender, combine the flour, sugar (I suggest using 1 tablespoon for savory crepes and 2 tablespoons for sweet crepes), salt, milk and eggs. Blend until smooth. Scrape the sides and add the melted butter. Blend again until smooth, scraping the sides as needed to incorporate all the flour. Refrigerate the batter for 30 minutes, or overnight.
Pour the vegetable oil into a 10-inch nonstick skillet over low heat. Let the pan preheat for 5 minutes (this will ensure that the crepes brown evenly). Take the crepe batter out of the fridge and give it a whisk (or you can re-blend it).
Once the pan is preheated, increase the heat to medium. Using a paper towel, rub the oil over the bottom of the pan (wipe out any excess oil). Pour in ⅓ cup of the batter and immediately swirl the pan to evenly coat the bottom (check out the video above to see how it's done!).
Cook the crepe until the edges are browned and the bottom is golden, about 30-60 seconds. Using a spatula, loosen the edge of the crêpe, then use your fingers to flip it over. Cook until golden on the other side, about 15 seconds.
Transfer the crêpe to a wire rack. Repeat with rest of batter, stacking the crêpes on top of one other as they’re finished. If needed, rub the bottom of the pan with a bit more oil if the crepes start to stick—this will depend on the pan you use (I usually don’t need to add more oil). Let the crepes cool completely.