Refineries are producing ONLY one line of diesel and it is formulated to just barely meet UltraLow diesel specifications mandated by EPA and based on ASTM standards.
Refineries don't like sulfur (it's kills catalysts) but it's prohibitively expensive to remove the last tiny bit.
Non-spec product (including diesel with too much sulfur) is run to slop tanks and then metered back into the incoming crude oil stream (actual input point back into the plant works varies by many factors day-to-day) to be re-refined through the plant.
Stickers put on bulk tanks are there only to protect the wholesaler and retailer from litigation / EPA in case somebody (me, for instance) checks a sample in a high-end NIST-traceable commercial lab.
Some refineries will install into their diesel stream at the sales point into tankers an admixture package if their customer is willing to pay for it. Similarly, some large regional wholesalers will custom blend admixtures into their diesel.
Some customers require a certain blended admixture package if they're running large fleets and control their own central-refueling bulk stocks. Trade journals are full of reports about how fleets have saved serious money by controlling their fuel stocks.
It's truly not difficult. Refineries will sell to anybody that shows up with a tanker and cash (actually, you have to open an account; but 'cash' in the sense that for a one-time purchase your bank account will be debited before you leave the loading rack) and blend packages are readily available. Just like propane: if you happen to need 10,000-gals, bring 'cash' and get loaded.
Basically, it comes down to (1) buy diesel at a location with high-turnover (2) store safely (3) filter filter filter obsessively (4) use a known quality product like Stanadyne especially in older high-sulfur machines running low-sulfur fuel.
Please post back your continuing experiences so we may all learn.
