This is the operative part of your post: "Sometimes the supplying jobber will do their own thing..."

So you never really know what you're going to get. On the other hand all Hess stations are required to get their supply directly from Hess. The quality is consistent and one of our members in Sarasota had a fuel sample tested that came out at 47 cetane.

My seat of the pants evaluation is that all three of my Diesels love Hess fuel. They run far better on it than any other petroleum based fuel.

Biodiesel, however, is even better. Just this week I started experimenting with Biodiesel from Ward Oil Company in Tampa. The 240D is running 100% bio and seems to be much quieter and smoother. The Jetta is on a 20% bio mix, again with a noticable reduction in noise. I drove it yesterday and would have mistaken it for a gasser if I didn't know better. The E300 hasn't had a dose yet.

So if you can get the Hess, definitely try that. And if you can get biodiesel, try a 10% to 20% mix for even more improvement.

__________________
Rick Miley
2014 Tesla Model S
2018 Tesla Model 3
2017 Nissan LEAF
Former MB: 99 E300, 86 190E 2.3, 87 300E, 80 240D, 82 204D Euro
Chain Elongation References