Aeromatic hub oil

A

Abisceglia

New member
It must just be my inability to properly search the forum as I'm sure this subject has been discussed many many many times... It seems Marvel Mystery Oil is unavailable in the great white north so I'm looking for an alternative for my prop hub. I understand a light weight gear oil is in order. Something like 75W90? There is also seepage from the seals. I heard this is somewhat normal for the Aeromatic?? I've also been told that adding STP will help stop the leaking. Thoughts??

Cheers
Andy
 
Andy, I don't know much about the Aeromatic prop but I do know a bit about Marvel Mystery Oil as I buy it by the case to feed my very thirsty old Chevy trucks. It's not going to slow down any leakage but it's good stuff from a lubrication standpoint. I don't think much of STP, but there is another product called "CD-2 Stop Leak" that might prove more effective - just make sure you are doing no harm! Not sure where you are that you can't get the MMO, but I buy it from Amazon - I think they ship anywhere... Rob
 
Thanks for the reply Rob, I'll look into Amazon. Conversely I think I'll give Arematic a call to se what the skinny is.
Cheers
 
Andrew, 75/90 is not very light weight and as you say, you live in the frozen north. I would suspect that it would not be good at all in the winter. I have never actually seen original Aeromatic Oil, but I think it is a rather light weight oil. Kent has recommended various oil over the years, so please let us know what you find out. I was told years ago that Automotive STOP LEAK TRANSMISSION FLUID would help since it is designed to soften up seals that have gone hard. Keep us posted. _____Grant.
 
Well, I used to have "Aeromatic Oil" as supplied by Univair....some 40 years ago. It looked like 30 SAE motor
oil as far as I could tell. The first Aeromatic I had way back then would leave a few speckles of oil on the windshield, but when I'd check the oil level every year, it would only take an ounce. I wish I'd kept the prop. It performed flawlessly!
Dan
 
Okay, I just got off the horn with Kent at Aeromatic and he offered some interesting insights. Firstly, he mentioned that using a 75-90 or any heavier type viscosity oil might induce hydraulic lock in the piston causing exactly what David Reid experienced, the prop snapping to full coarse. Probably not too likely in the summer months but as the viscosity thickens in the colder mornings it may be an issue.
As far as what to use, really any light gear oil or even 3 in 1 machine oil would work as long as it's safe for use with nitrile seals. When it comes to reducing or stopping leaks, Kent mentioned using Lucas heavy duty oil stabilizer. Another good product he mentioned was Granvilles Strut Sealant, says even the airlines use it to stop leaks on their landing gear. He says a thimble full is all that's needed. I checked and Aircraft spruce carries it.
I plan on using it so will report back once I get things buttoned back up.
 
I use to have some actual Aeromatic Oil, and it was very light wt. Almost like 3 In 1 as I remember. I also was told by one of the previous owners of the design ( don't remember which one now) to use heavy duty gear oil as previously posted. Don't think I actually used it...but I still have some on the shelf.
Marvel Mystery oil is a solvent based product. Years ago, Aviation Consumer ran some on a GC Mass Spec and that is what they found. I have used it ' cause I also drank the cool aid and wanted it to work. I think it is really just foo foo dust, and if anything the results are almost like the placebo effect on med trials...it works 'cause you want it to work! I have yet to see actual engineering data that shows it really does anything! That being said...anyone want to buy a gallon that is also on one of my hangar shelves?
Hmmm- should I have put the previous paragraph in a separate thread?
 
Oops! Never mind, it's just the can. Says the oil has "thickened", and not to use in a prop.
Got so excited seeing such an ancient substance listed, I jumped too quick to this forum.
 
Several years ago (maybe decades) there was discussion about this oil and there was a mil-spec number given that nobody seemed able to find on the private market. If that number could be located, I would think that any big oil supplier could sell you a similar substitute. That mil-spec number might even have been in one of the Aeromatic manuals. _____Grant.
 
Well I did as I said I would, and filled the hub with 0W20 along with the Granvilles Strut seal conditioner. I've not flown behind it yet but run-up has shown no further leaking from the seals.
I've installed the nose bowl mounting plate, (thanks Grant) so will button things up and go fly. Incidentally, while changing the plugs I scared myself on the last plug, T1. Always the last one eh? As I pulled the old plug out a helicoil came with it. I didn't realize the Franklin's sparkplug ports were designed with them. Anyway non-event, new one installed and ready for flight.
 
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