Hi 3lr,
Well, if you listen to the right people you might end up trying to put medical nitroglycerin pills in your tank along with all sorts of crazy or otherwise ineffectual stuff. Don't try that but do go and watch the movie, "The World's Fastest Indian" if you have not already seen it
A great place to get some alt fueling grounding is the book, "Sliding Home" by Ray Holan. He covers pretty much all your blending options from xylene to tuloene, acetone, pure gum turpentine and plenty others. I think it is maybe $20 with S&H - well worth it!
Naphtha is commonly available as varnish makers and painters (VM&P) naphtha in any hardware store. Could be wrong here, but I think naphthalenes are also what comprise Petroleum ether, but don't quote me on that! Naphtha makes an excellent purging liquid if applied properly to your injectors but i rarely find it cheaply enough to use as a fuel. As a non-fossil fuel additive which has a very high cetane rating, try pure gum turpentine. It is made from the resin of pine trees and also makes a good injector purging liquid.
Please don't go throwing any old hydrocarbon in your tank. If you were awake in chemistry class you might remember that "hydrocarbons" are many. Diamonds are hydrocarbons for example. Am not talking carbon emissions, but as for liquid hydrocarbons, lots and lots of them are toxic in and of themselves. Toxic, like carcinogenic and mutagenic, like benzene which is in gasoline. The emissions created by combusting hydrocarbon blends are often even worse than the individual constituents. But please don't take my word for it, the peer reviewed research has been done and is available through your library. Likely very expensive over the internet (like $30 for 48 hour access)
Something useful which can be said of all hydrocarbon liquids, toxic or not - they are all organic
Anyways, I hope this information helps you with your predictions about the liquid hydrocarbon in question, others and any or all of their augmenting and diminishing characteristics as diesel fuel constituents. On that note, I would be especially wary of performing practical experiments on post 2000 DI's which are still under warranty coverage.
What are you driving?
Best,
-Patrick