Early bicycles always employed oil, rather that grease.
Grease is merely a form of thickened oil, thickened so it will not run out. Oil is the lubricant, not the grease-base.
Grease is generally a cooked concoction of some form of metallic soap, plus some sort of
Q: what is a non-fixed oil? A: any petroleum oil is a non-fixed oil; it can be distilled from crude petroleum,
it can be a partial blend of any of hundreds of variants that make up thick, black crude oil;
it is, at best, a satisfactory lubricant because it does not turn acidic with age, but it will oxidize
if not doped with various chemicals. Straight-run oils eventually gum.
Q: what is a fixed oil? A: any animal or vegetable oil of recent (not ancient) origin, which can be eaten,
or used to lubricate machinery. It is called "fixed" because such oils cannot be "cracked" nor distilled.
They are no longer much used for machinery, though some of them are superior lubricants (castor oil, lard oil),
because the animal oils, in particular, go rancid with age and exposure, becoming acidic, and therefore, detrimental
to any kind of metal other than the noble metals.
Q: why is grease of use today in bicycles? A: for convenience and cleanliness.
Grease for ball bearings is inferior to the old time bike's universal, but dirt-aquiring, use of oil squirted into oil cups and oil holes.
Oiled bearings can and are flushed clean by addition of fresh oil. The bike, though, becomes a dirt-magnet
as the oil creeps from the hubs and bottom bracket, in particular. Wipe with a soft cloth, or use, on the small hub
of olden times, a leather thong-device, that polishes and sops the weeping oil from running down the spokes.
Q: How does grease or oil lubricate at low surface speeds? A: by "boundary lubrication", oily-ness.
Q: Which is more "oily", truly? A: Oil of the specific type best for the application.
Q: What "body" of oil is best for a particular purpose? A: An oil just thick enough to do it job;
too thick and it makes excessive fluid friction. Additionally, all oils and greases, other than some
highly developed synthetic lubricants (not of petroleum origin) thicken in extreme cold, and thin in extreme heat.
All lubricants thicken or thin with temperature.
Q: My bike has greased "sealed" bearings. How can I best maintain them?
A: Do nothing but to add a drop of heavy bodied, synthetic oil (it won't wash off like dino oils) to the lip "seal"
of the sealed bearing, which, in fact, is not really sealed. Q: Why? A: To prevent ingress of water over time,
and to lubricate the rubber "seal" so it does not rub itself worn, and then let in road grit and water.
Aside from that, there is no servicing needed for modern bike's "sealed" ball bearings.
It is suggested to apply a drop of oil to all "sealed" points accessible, upon occasion, particularly just before
washing a bike. This ensures, better, that no water will suck into the "sealed bearing".
Q: My bike is black and in the hot sun. Should I hose it down without first oiling the "sealed" bearings with
drops of synthetic oil, or oil of any sort?
A: In my opinion, NO. Q: Why not? Because the hot bearing will be suddenly chilled, and will, therefore,
create in itself, a partial vacuum, and thus, "inhale" a minute amount of water.
Q: Of what harm would that be, then? A: The "ingested" water, no matter how little, will emulsify with the grease,
and make the grease less of a lubricant. Also, some minute amount of silica road dust will go into the bearing.
Q: If, by pulling a crank arm and chainwheel, I can -see- the "seal" of the bearing. What would make a good preventive maintenance procedure?
A: Inject grease of the maker's specification, into the bearing, using a grease-injection hypo needle, taking care
to not damage the "seal" (which is merely a sort of poor shield, not a true seal).
---tbc: Why are cup and cone bearings of the past, actually superior for bike service, if maintained properly?
This essay will come some other day. Enough for now.
Bacon grease is good for sliding surfaces, but it will soon eat the metal.
Early engines, however, ran for over a century, using NO petroleum oils of any sort;
the maintenance men renewed the animal or vegetable lubricants used pre-1860, regularly,
to prevent acid-attack of the metals. Steam engines still employ "fixed" oils in their steam oil supply.
Why? because these fixed oils are the only oils that can withstand both great heat, and work (lubricate well)
when mixed with water.