And I thought I was anal about that stuff ! !
But seriously, like Pete said, anything is better than the (next to) nothing you get with ULSD fuel these days. I believe one important factor that gets overlooked is the moisture / condensation / water aspect, especially if you have lost the WIF sensor somewhere along the line.
Fastalker also makes a good point about the off-the-shelf stuff. Those manufacturers know people are just dumping this stuff in their tanks and burning it. Some of it is probably just snake oil. There was a study done a couple years ago and posted all over the Internet showing a wide margin of results from the different fuel additives out there.
The point is, "oil," in it's MANY forms and formulations, is a natural lubricant. Motor oils, ATF fluids and gear oils normally have the additives and FMs used up or chemically decomposed by the time you drain it. Personally, I run everything through the Cummins in a homebrew mix. WMO, ATF, Power Steering, Hydraulic, gear oil, whatever. If it started out as some form of oil in one of my pieces of equipment or vehicles, it eventually gets burned in the old Dodge truck. But that is after it is filtered (sub micronic) and mixed back in with about 30% 2-stroke, and a dose of either Fuel Power (Summer) or white bottle Diesel Kleen (winter) at an overall 2-3% add ratio (half gallon per tank).
I would not worry about it unless you are megadosing (20-50%) oil. In that case, I'd be a little more careful about what you're putting in there, in terms of filtration and exactly what it started out to be, and what happened to it before you got ahold of it.