Firstly, all coffee beans have oils naturally present. Those oils are basically released during and after the roasting process, specifically after what roasters call the “second crack”. The amount of oil can be a result of the roasting time - longer, darker roasts will release more of the oils - or consequently, the freshness of the beans. After a period of weeks or months more oils will seep out until stale beans actually may become dull.
How do I figure out which coffee beans are right for my coffee machine? That’s the question most people want to answer. Firstly, the “best” beans are often those that make coffee that suits your own palate. Yours, not your neighbor’s, your best friend’s, your barista’s or a blogger’s (me included). But the best advice is to find an experienced local roaster. Experienced since the number of new roasters popping up tends to suggest some are more knowledgeable than others.
For espresso based drinks from your Jura, a darker roast is preferable. But it does not stop there. There are different traditions amongst dark roasts - Italian, French, etc.
The beans I use come from a boutique Texas roaster established 40 years ago. They are designated as a Premium Espresso Blend and suit my preference, which is a French roast. There is rarely much of a sign of oils but the truth is, I have never had issues with my various Jura machines in almost 20 years.
It is important to consider two characteristics pertaining to commercially produced beans. Not to say that some well known brands, especially those from Europe, are not good quality. The truth is that those companies we see on grocery store shelves buy beans in very large quantities. More often than not, the very best green coffee is not available in sufficient volume to satisfy demand. Another thing that can happen is that a blend of lower quality coffee beans is over-roasted, simply to mask the true flavors. Hence a “burnt” taste.
So back to the original question. What are the criteria when it comes to deciding if beans are too oily for your Jura? My answer would be a combination of two factors. Firstly, build trust in your resource - the local roaster - buy good quality and don’t skimp on price. Your cup of Joe is going to cost in total less than a dollar in ingredients in a Jura coffee machine. Adjust your grinder according to the roast - finer for lighter roasts, more towards medium for darker roasts. Keep your beans for no more than a month, in an airtight container. Any sign of a change in appearance, from a slight shine to excessive coating of oil and you might want to think twice about freshness. Above all, buy good beans and enjoy your coffee - don't be anxious.