Former barista here! This is what that is. Different machines using different roasts, water, settings, etc. will extract differently, resulting in different oil amounts.
It definitely might, water chemistry changes extraction so much there are coffee nerds who add tablets to distilled water to get the right composition to brew with.
Whatever your thoughts on that is, distilled water is not optimal if you want to extract coffee.
You know the little oily colorful sheen on the top of a cup of coffee?
At one point just at random I made a pot of coffee from a jug of distilled water I had, instead of the filtered tap water.
It had no little colorful sheen.
I have no idea if it’s a big deal or not, but it made me legitimately concerned.
I thought the sheen was from oils naturally present in the beans.
Former barista here! This is what that is. Different machines using different roasts, water, settings, etc. will extract differently, resulting in different oil amounts.
That was my understanding, as well. I can only report to you what I observed.
Maybe something present in the tapwater allows more oil to be drawn out?
It definitely might, water chemistry changes extraction so much there are coffee nerds who add tablets to distilled water to get the right composition to brew with. Whatever your thoughts on that is, distilled water is not optimal if you want to extract coffee.
The filter type also changes the oil content, for example paper filters absorb much more oil than metal filters
Filtered water will extract less due to a lack of trace minerals.