The manufacturer of every gun I own puts in it's owner's manual that the gun is to be lubricated with a "Light Machine Oil" or "High Quality Firearms Oil". I did not make the choice to follow this recommendation for economic reasons although using a Light Machine Oil is a very economical proposition.
I also note that I did use motor oil on certain inaccessible locations since I believed the motor oil would not be as liable to migrate as the light machine oil.
As to "informal test results", I have the longest term "test" that I have seen referenced on this site. In 1993, I routinely cleaned and oiled my guns and put them in the gun safe. Later that year, I was stricken my a neurological disease that handicapped me. Between 1993 and 2014, the safe was opened on rare occasion and various guns shown to other people before being returned to the safe without the guns being wiped down or the lubricant being refreshed. In 2014, after successful treatment, I was able to return to my guns. They had suffered no rust, corrosion, or other deterioration in the intervening 21 years.
So, I didn't use the gun-specific products John and others touted, like BreakFree CLP. I didn't consult with unnamed experts. Instead, I used the "Light Machine Oil" that the manufacturers (who presumably have some expertise in caring for their own product) said to use and it worked perfectly well far longer than I would have imagined it would.
Finally, the belief that the motor oil would not migrate was borne out. Even though the rifles whose barrels were libricated with motor oil were stored in a muzzle-up position, the oil did not run down the barrel onto the wood or plastic furniture even after 21 years.
