automotive lubricants (ATF, manual trans fluid, or heavy motor oil) as bike chain lube? Good afternoon,

I'm quite mechanically inclined (formerly an auto mechanic and currently an engineer) but relatively new to cycling.  Compared to other contexts I'm familiar with, I've noticed that bike chain lubricants, for example the Park Tool chain lube (https://www.amazon.com/Park-Tool-Synthetic-Blend-Bottle/dp/B000AOA290) or the Finish Line wet chain lube (https://www.amazon.com/Finish-Line-Bicycle-Chain-Lube/dp/B000WYCD5O?th=1) are very expensive per quantity compared to automotive lubricants.  I'm wondering if anybody has extensively tried any of the following as bike chain lubricant:

-Automotive Transmission Fluid (ATF)

-Manual Transmission Fluid / Transfer Case Fluid / Gear Oil

-relatively "heavy" motor oil, ex. 10W-40

In my general experience I've found that ATF is usually the best lubricant for almost any purpose, for example I've found that ATF lubricates air tools better than air tool specific lubricants.

I'm planning on trying ATF out before I spring for another bottle of Park or Finish Line chain lube.  Has anybody else tried any of the above for bike chain lubrication?
In my experience, the objective of a good chain lub for a bike is to maximize lubrication time while minimizing dirt attraction.

That happens for three reasons:


The chain is totally exposed in a performance bike. You have dirt coming from the ground, the wheels, the air...
You legs are surprisingly close to the chain, and may rub it quite easily.
The situation where your chain snaps from the crankset and you may have to reinsert it manually in the crank teeth is not quite rare.


That is why there are a great variety of chain lubs. You can go from minimum dirt attraction (wax) to the maximum (wet).

I would say that if you are perfectly happy with a wet lub, a switch to an ATF one would not pose a big problem. What you do not want to you use are solvents, most notably WD-40, they do not act as a lube long enough.

Do not use thicker oils, as standard engine oil: they will render your chain a mess in not so long and they won't penetrate deep enough in the links.

On the other hand, if you want to minimize dirt attraction, something I prefer personally, I would use a bike chain specific dry lube or wax.

As a bottom line, you know that a 120mL bottle lasts like forever? You have to apply only one drop per link, meaning only 0.05mL per link.