Bees And Hummingbirds
According to Cornell Lab of Ornithology, the best way to discourage bees from feeding from a hummingbird feeder is to buy a hummingbird feeder with bee guards, made of plastic mesh, that keeps bees and wasps away from the feeding port. An even better defense is to buy a saucer-shaped feeder, from which the birds feed through ports in the top. This type is inherently bee and wasp-proof because the nectar level is usually too low for insects to reach, but easily in range of the shortest hummingbird tongues.
If the insects persist, try moving the feeder. They may never find it in its new location, whereas the hummingbirds will quickly find it again. If that doesn't work, take the feeder down for a day or two, until you stop seeing bees and wasps looking for it. The hummingbirds will look for it, too, but they won't give up nearly as soon as the insects will.
Using a vegetable oil spray may attract other insects or may get on a hummingbird's body and cause them harm.