So, the other night, I was re-reading "The Grapes of Wrath." At one point in the story, the Joad family stops at a service station and, among other things, purchase two one one half gallons of "cheap, black motor oil." This kinda stuck with me. I've never seen black new motor oil in my life. I'm wondering. Since this novel was written in the 30's, was oil less refined in those days and therefore, black? Would it have contained at least trace amounts of gasoline, diesel, kerosene etc, since it was less refined? Did they simply pump it out of the ground and into cans and sell it cheap? When did they stop selling this kind of oil and when did they start dying oil in the various shades and hues we see today? Inquiring minds want to know.