On the topic of diesel.
Most of the major players are pretty good about their diesel. The formulation typically changes every two weeks.
During fall based on the formulation it might be prudent to fill every two weeks to be blending the fuel formulated for the colder weather. In spring the same holds true to make sure you are topped up with the colder weather fuel in case a freak cold snap catches everyone off guard.
I have noticed that some diesel from Flying J not performing very well in winter which makes me suspect since they are a US chain that they were selling summer diesel in the fall which led to very subpar mileage.
Personally I like the Shell V-Max Diesel.