There are several problems. . . besides the fact that I have never heard anyone say that the loeffler 250 prop was good but besides that.
1. If you really beleive that it is 250mg/ml then evaporating any BA will cause the prop to precipitate out of the oil thus making is mg.ml content less dependent upon how much has evaporated. The reason for high BA content in high mg/ml gear is to be able to put the high quantity of gear into a ml. (T400, any high prop, ect.)
2. Unsterile oil is just that unsterile. I wouldn't use anything that was unsterile in my body. Some argue that BA, being an anti-microbila as well as a solvent will kill all the contamination but you may be dealing with other contamination from other souces besides microbes.
The only thing I would suggest (if the product is what it says it is) is to mix it with sterile oil or anther type of gear.
If it was me I would get a 10cc
syringe draw all the prop up into it and inject it in the toilet. ;) Then buy some decent stuff. I'm willing to conceed my opinion if there is just one person that actually liked the 250 prop and had good results. (I haven't even heard of anybody even finishing a bottle) I don't know first hand and never will so I realy don't know.
Peace. Freez.