Best brand of diesel for W123?

[79-240d]

I've had my '79 240D for around a month now. Filled it up for the second time last night.

The first time I filled it up, I went to Shell.

Last night, I filled up at Arco (I'm in the Los Angeles area). I could swear that from the moment I started it after filling it last night, the engine is not running nearly as smoothly. Idle seems rougher, acceleration (which, as everyone knows, is not exactly strong on the 240D in the first place) is weaker, etc.

1. Is this just my imagination, or have others found that fuel from different refineries makes a noticeable difference in how their cars run?

2. If there is a difference, what brands do people find to be better for their W123s?