November 24, 2022 -

IMPORTANT NOTE : For most customer facing shops, I would continue to use Shimano Mineral to avoid any issues with customers, warranty, etc. and purely from if anything goes wrong, I have a ground to stand on perspective. Saving a few dollars is probably not worth it for most of you.

Backstory - During the COVID 19 pandemic, while I was still working full time at a shop, we all experienced different shortages. There was a weird period of time where Mineral Oil was unobtanium and was on backorder for months this led me down a rabbit hole of looking for alternatives.

DISCLAIMER : I do not have any background whatsoever in chemical or petroleum. but I do like science and research. This is just a compilation of all the data I haves scraped from the web so that those who are falling into this rabbit hole have a slightly easier time understanding all this.

The Product - Mineral oil is a bit of misnomer. What Shimano sells in a bottle is a hydraulic fluid. Shimano's own safety datasheet gives us insights into what it actually is:

https://si.shimano.com/pdfs/compliance/sds/hydraulic%20mineral%20oil-202008-ENG-GHS.pdf

Page 9 has the part we are interested in.

Shimano Mineral Oil = Shell Tellus C8

Some googling reveals that :Tellus = mineral oil based hydraulic fluid (as opposed to synthetic, mixing mineral and synthetic is a big no-no as seal compatibility could be an issue)

C = Mild anti-wear additive

Quick research shows that there are three main types of additives that these hydraulic fluids usually have :

1. Anti oxidization

2. Anti wear

3. Detergent

Their roles are pretty self explanatory.

8 = Kinematic Viscosity at 40C (in cSt or mm^2/s)

8 is the interesting number as it tells us how 'thick' the stuff is (lower number flows like water, higher number is 'thick' like honey). As most of you probably know, oils usually get thicker when cold. Most manufacturers measure the viscosity at 40C and 100C.

So essentially, Shimano obviously does not manufacture their hydraulic oil (duh). They buy it from Shell in giant drum loads, package them into a bottle and sell it to you at a hefty markup. some more wild googling shows that Tellus C10 is the closest commercially available product, that was only sold in Asia and can not be easily sourced here in Canada.

Alternatives - So essentially, it's just a mineral oil based hydraulic fluid. We don't want synthetic. It has some additives in it. We don't want the additives to react with seals and the bladder. We want it to be close ish in dynamic viscosity so that it doesn't cause weird lever feel or something like that.

People run all sorts of shit in their bikes. You can probably piss in it and it will probably work fine for a short time. However, two options really stood out to me as a good long term solution.

Contender #1 - Total LHM+

Citroen and some older Rolls, Bentleys use these because the French are weird and the English are mad.

A lot of people swear by LHM+

But the stuff is a bit thick at 19cSt at 40C

https://www.morrislubricants.co.uk/products/87_5f1ff98dae430.pdf

and more importantly the safety sheets show slightly different list of additives compared to Shimano stuff.

https://static1.squarespace.com/static/583398a9893fc0fa3cc8c018/t/5859a4e6893fc05cfa48efd9/1482269927509/LHM+Plus+MSDS.pdf

LHM+ Safety Datasheet

Shimano Mineral Oil Safety Datasheet

The fact that a lot of people are running this stuff without any issue and seem happy with it tells me that all the ingredients in the LMS+ are compatible with all the rubber seals and bladders. Now are all these additives better or worse than the Shimano stuff? I don't know.

Contender #2 - Aeroshell Fluid 41

Aeroshell Fluid 41 seems to be a close cousin of the Shimano Mineral Oil

Less people run this stuff because it's harder to come by. I really liked this option because :

1. It's dyed red. Definitely darker than Shimano pink but seeing that green can sometimes make people raise eyebrows the slightly darker red gives you a bit of plausible deniability

2. It's made by Shell, the same company that makes the Shimano stuff.

3. It has lower Dynamic Viscosity than the LMH+ and closer to the Shimano stuff.

4. Additives in the ingredients list are similar to the Shimano stuff.

5. There is a aircraft supply store in a small regional airport close to me that sells this stuff for 10 Canadian pesos per quart/L (https://canadianairparts.com/ if you are in Vancouver or https://www.aircraftspruce.ca/ if you are in Toronto/Hamilton).

6. Now I can say I run aerospace quality fluid in my bike.

Aeroshell 41 is hydraulic fluid used to run brakes and flaps mostly on smaller aircrafts (like small Cessna kind). So the application fits the bill.

At 14.1-15.7 Cst (1Cst = 1 mm^2/s), it is a bit closer to Shimano stuff's 8 and is thinner than LHM+ 's 18.

Kinematic viscosity of AeroShell 41

More importantly, the MSDS shows similar ingredients to the Shimano stuff.

Aeroshell 41 Safety Datasheet Shimano Mineral Oil Safety Datasheet

Of course you get the limited picture from the MSDS but it seems they are similar in nature.

Now aside from the colour, the most noticeable difference between the Shimano stuff and Aeroshell 41 is the smell. The Aeroshell 41 and has much stronger petroleum smell than the Shimano. I think this comes from that difference in base oil between the two.

Results - in the end, the shop I worked at ended up sourcing the genuine stuff from another shop that had a few left and we used that till they came back in stock.

However I bought two quarts (~ 2L) for my own personal use and have bled about 10 bikes with it so far.

At this point some of the bikes that I have bled with Aeroshell 41 has been running it for over a year and the result is... quite boring. Nothing interesting. It works, didn't break down, Didn't cause up the seals and bladder to swell up and do weird things and still feels just like it has been bled with the original stuff.

This is somewhat expected as loads of people have already tried it and have reported the same.

TLDR : You can run Aeroshell 41 instead of Shimano Oil and it's about 1/3 of the price for similar list of ingredients and made by the same company. But it smells way stronger and is a bit darker in colour. This could cause some issues with some really keen customers or warranty down the line so I wouldn't recommend it for shop use.

Thanks for reading!