I'm not a fan of using anything oily in hot weather. I use dormant oil spray on my orchids but only in winter if the weather is really cool, highs below 70F.
You'd have to leave an oil spray on to smother new generations or use it again and again, same as soap. Plus you'd also have to wash it off the plants so they wouldn't become photosensitive.
I'm a BIG fan of the KISS theory. Plain old soap works well, for an initial infestation and then just spraying with water keeps them away beautifully in my garden.
