Only the crudest of fractional distillation was practiced in the 1920s - to what was referred to as "light", "medium" and "heavy" viscosities - which could (and often did) mean different things to different oil companies. I seem to recall reading somewhere that the further "refining" of petroleum in that era consisted of crude filtration through a clay bed at best. Chemically, most of the oils available were an abomination of sulfer contaminents, acids, asphaltics, and strongly polar aromatics mixed in with the petroleum as it came from the ground. (The stuff we recycle after just 3,000 miles would've been considered pristine in comparison.) The best quality oil from the ground was generally considered Pennsylvania sourced crude, hence its reputation that endured well into the '70s. Oil from Pennsylvania fields went on to become at least unofficially recognized as a "grade" and eagerly sought by the motoring public in the know. Like any unofficial title, time (and money from area oil field operators acting in enlightened self-interest as a co-operative) bestows "official" recognition eventually. By the mid-to-late twenties, acid treating and sulfer dioxide treating helped tame the worst chemical contimants. Also remember there were NO additive packs in the motor oils of the time. Multiweight? Ya' gotta be kidding... The irony is that aircraft engines were not filled with this crap. Instead castor bean oil was used. It was purer, it had fantastic lubricity, and it withstood heat with near zero chemical breakdown (at least while hot...). And, being a vegetable product, castor oil is a naturally occuring ESTER! (And, one of castor oil's better known effects on the mammalian gastric system negated any need for warnings regarding thoroughly washing up after coming in contact with the stuff. Any shade-tree mechanic of the era who got that stuff on his hands just once WOULD forever after remember to wash before eating...) So, why not castor oil for general use in passenger cars and light trucks? Well, it was used in race cars. However once heated to operating temperature and then allowed to cool, castor oil has a nasty habit of polymerizing into a semi-solid goo that has to be scooped out of the sump and practically chisled off any parts it's adhered to. For racing and aircraft use, no biggie - there'd be a pit or ground crew ready to change the oil out before it cooled and glopped up with perhaps a refill and brief spin-up to suspend any remaining original fill, and then another drain and final fill. However, John Quincy, and his lovely wife, Ethel Mae, residing in the wintery wilds of Michigan or Minnisota usually didn't have that luxury (or in many cases, that of a garage or indoor plumbing, either...).
[ June 20, 2004, 11:19 PM: Message edited by: Ray H ]