After a while I settled on the beans that for filtered coffee, and I like espresso with them too, just ground more finely. So now I tried Turkish coffee with the same beans and the same grind as espresso, and, well, it doesn't seem to taste as well as I expected. Sort of more oily than espresso. What would be the prime thing to try change? Any special beans required for optimal taste?
I believe many people simply boil the grounds in their earlier attempts. This approach is known not to be a good practice.
Based on my experience, I could say the most notable changes that you could note in Turkish coffee is twofold: it should be fresh and quick.
Freshness is important as the grounds are as fine as flour. So, they stale very quickly. One of the reasons that people have traditional hand grinders is this. Ground just before you prepare.
Quick preparation is important to be able to extract more before the all the flavor has been evaporated. That's why you need a pretty good cezve with a decent stove to transfer heat as quickly as possible. It is said that whole preparation must take under two minutes.
OF course there are many details regarding any kind of coffee preparation. I believe these two could be the first things to change. Unfortunately, Turkish coffee preparation requires serious experience and the learning curve is steep. You could fine tune many parameters after gaining some more experience.
For similar discussion that may include a hint please see:
I assume your espresso blend is a dark roast. Try light roasts for Turkish. The extremely fine grind can lead to overextraction of dark roasts when using the Turkish method.
Additionally, double check your method. You haven't provided details of your method or grind size, so I can't comment on that. Still, using dark roasts could cause that oily taste you describe, so try switching to light roast first and foremost.
Definitely, you need to use a different grain of different roast for each type of cooking. After all, all this will affect his taste. Plus, you can always make coffee to your liking. For example, you like a thick and bitter espresso, while Chemex is more fruity and sour. Than one type of grain will definitely not suit you.