Mineral spirits.
Better minds than mine went into this a year or two ago and determined that Lee's Liquid Alox is Alox 350 thinned with mineral spirits. A couple of them even wrangled samples from the maker and made their own. If any of you work for car dealerships, the stuff is more commonly used as undercoating.
Alox 350 is sometimes available in five gallon buckets at a few of their distribution points, but it's generally sold in 55 gallon drums. I looked into buying some, but the shipping would ruin me.
Anyway, it having to be blended and the volatility of the mineral spirits explains the varying consistencies we get. If I ever lay my hands on ALOX 350, I'll do my blending outside with a yard sale mixer because of flammability.