An interesting story about Stanadyne, for what its worth...
A few years ago in the TDR magazine, an article was done about diesel additives and highlighted a product from Amalgamated, Inc. They make diesel additives in huge volumes for fleet use and so forth. Many of you are familiar with that issue, I'm sure.
I called Gary at Amalgamated and ordered a pail (5 gal) of the "TDR blend" at that time. I asked him about Stanadyne. He said Amalgamated was originally chosen by Stanadyne to provide the additive to be sold under the Stanadyne label. However, when Stanadyne got the "bill", they thought it was too much (too sophisticated of a formula - too much stuff in it). They wanted it "simplified" to save $. Amalgamated wouldn't do it. So Stanadyne found another source. The stuff you can get from Amalgamated is what Stanadyne didn't want.
At least, that's roughly how I remember the conversation went. In any case, I've been using Amalgamated every tank full since that article came out. So far so good. A couple of times I've run a few tanks in a row with no additive. Didn't see much mileage difference. But the engine seemed a little louder after the first tank. Could be my imagination.
Since you'll want to know, a 5 gal pail goes for about $90 to your door (lower 48). That was as of the last time I ordered it (last spring). I use 1 oz to each 3 gal of fuel, roughly.
Search for Amalgamated and you'll get a evening's worth of reading, though a lot of that is folks wanting to know how to split a pail or how its working out in daily use.
-Jay