Why would using oil make muffins less sweet? I've been wondering, what makes muffins less sweet when using oil? (instead of butter?)
In this case, a muffin mix tells me to use butter. The alternative (to make "american style" muffins) is to use (sunflower)oil. It would make it less sweet.
I think you are looking at it the wrong way... butter makes it sweeter, so not using butter is naturally "less sweet". It isn't that the oil 'causes' less sweetness.