May have changed but ten or more years back. I found much less diesel fuel milage with one brand of fuel. Tried two tankfulls well separated with the same results. Others told me they experienced the same issue with that brand.

This too may be a problem you will never see at busy truck stop locations. Many of those truckers almost lived on their fuel milage.

This thread reminded me that since winter is coming. I should have a look around the older 2006 volkswagon tdi we acquired. I hope Volkswagon did not drop their decent water separator.

In my extensive travels in America many years ago now. I never observed any real difference between the diesel fuel sold there and in Canada.

This is also getting into the time of year for people that live in the colder climates. To land up with summer fuel and gelling problems if they purchase from small volume suppliers.