Hughe 300 used commercial transmission oil and truck fifth wheel grease (Shell Alvania) for the engine drive shaft.
S76 used Dexron II in the main gearbox, automotive transmission fluid.
I dont see a problem with using commercial parts if suitable. Its the price mark up that is the problem!!!

Nothing wrong with the use of non aviation specific parts if approved by the authority, once flew a brand new fixed wing whose production fuel cap came from a Ford Falcon as did the coil spring used on the nose wheel. The Dextron oil was developed for GM and its automatic transmissions, we had problems using it in the 76 as after some hours had been accrued in hot weather we suffered a loss of oil pressure yet the oil still passed all the specification tests, presumption by the scientific folk was that in being forced through the transmission oil jets the long chain molecules were being chopped into shorter chains, I'd have thought that would make for a loss of viscosity but apparently not. We swapped to Mobil Jet, no further problems.

Many air conditioning compressor and condenser are rebadged Denso.

The 3 dynamic absorbers in the nose & under the cockpit seats of a CH-47 were no fun to replace - heavy & awkward. Sounds like they finally got rid of them in the F models & are using a much lighter active unit.

Whirlwind Intermediate (Inclined) Gearbox mounting bolt - wire-locking! - 2 inches away from a 1 inch hole…

Chinook Mk1/D hyd and lube flexible pipe routes around the Aft XMSN….Wha!!!!

A bit off thread, but there was a famous case in the RAF when the venerable Whirlwind was still on SAR duties. A new fitter straight out of training reported in, and the sergeant said, "Right lad go and do a Kerosene wash on that engine" so lad goes and gets a compressor wash rig, and fills it with neat Kerosine, after fitting the rig to the engine, the pilot says OK after lighting to ground idle, the lad turns the rig on full, the result can be imagined.
It was the sergeant who got the severe rep, he should have checked the lad knew what he was doing.

Another much older RAF story is of a fitter cleaning a Magneto in a bucket of Avgas, he spun it over, thus destroying an aircraft.

There was a more recent event in UK where an EC135 was severely damaged when the comp wash was carried out using waste Jet A1 rather than de-ionised water by mistake!

Purge greasing the rotor head of the 212... one tube in each grip... my hands still hurts from squeezing so many times in a row...

I dont know which would be considered worse, wiping oil and changing seals regularly on a oil lubed head or having to purge grease on occassion. Having done both I think I'll stick to purging grease.

Greaed Heads....ah....memories of bales of greasy rags from wiping down Alouette and Llama rotor heads.....tail booms and tail rotors.

Then there was the added pleasure of undoing the mess and out of balance issues from leaking grease seals.

Loved flying them....but rag wiping was a full time job it seemed.

They were the only aircraft I ever worked on that reminded me of working on diesel engines: oil, grease, and fuel. And not to mention the task of changing TR stack bearing in the bush and having to wait for the cook to finish the morning bread before we could commandeer his oven to heat the bearing housings.

Ah yes.....the stack bearings and do remember the put the tail rotor blades on in the correct direction of rotation!