Originally Posted By: racin4ds
I find this funny as I see the same truck that fills the supposed top tier Shell station, go a few miles down the road and fill the non-top tier Circle K or other mom and pop station...
All this is is marketing, allowing these "Branded" stations to mark up the price of fuel.
The Top Tier additive package is usually mixed in by the tanker operator during storage tank fill. It's not much volume-wise, a quart or two will treat an entire tanker load. It's true that one refinery will usually service everyone in the area, but the additive packages do differ.
It's pretty much what you are paying for versus discount resellers. All fuel will have a basic additive package from the refinery, so discount fuel is not junk anymore than Top Tier is gold but there is a difference.
VW has a lot of data showing the value of the additive packages in engines that were dyno-run for many hours (equivalent to miles) if you're interested in seeking out some test results that are accessible from the internet without having to pony up for an SAE membership or don't want to pay hundreds of $ for research papers.
Somewhat back on topic, I'd be curious to learn what would make a Diesel fuel "Top Tier" as it's a very different animal in a very different environment than gasoline. Thanks for the heads-up, I might check it out when I have more time.