Vintage DD turntables. Are we living dangerously?

Minh,

You could use the 5W20 in both oils.
Good enough for this application, in my mind.
Just make sure to clean and dry the bottom plug/oil pan and the spindle/bearing from the RP well as it tends to adhere to metal parts and maintain its lubricity.

Re the formulation of synthetic oils:
For most oil companies, oil is a by product of refining crude to fuels.
It's a thorn in their side. They buy an additive package from companies like Lubrizol who specializes in this field. The additive package will contain, anti rust and oxidation agents, anti foaming, metal deactivators, viscosity modifiers, etc, etc.
Then, oil companies will package it nicely, put a photo of a tiger or a race car or whatever and sell it with all sorts of marketing claims...
Synthetics are a bit different in the sense that the base stock is manufactured by cracking ethylene to a long chain of hydrocarbons which do not contain impurities like in the case of standard mineral oil.
The main advantage of synthetic base stock is prolonged life and flatter viscosity curve (less change in viscosity as the temperature changes, which is desirable).
Both kinds will be blended with the additive package.
Royal Purple started as an industrial oil blending facility with two main advantages:
1. They filter and clean their base synthetic stock to a high level (ISO cleanliness of 14/13/11) - most important in process compressors and rotating equipment in general.
2. They blend their own additive package and in it, they include their secret recipe to a potent anti wear agent which increases film strength and reduces friction to a very high degree.
Of course the world is full of marketing claims, snake oil and $20,000 speaker cables which makes any claim a suspect,
I just have very good experience with RP in the industrial realm, which instigated my curiosity re my audio hobby, specifically my turntable bearing (both my previous Oracle Delphi and now my TT-101).

Btw, I am not an RP representative.
I am a chemical engineer who deals with mechanical seals and rotating equipment in general.

Halcro,
The purpose of a mat is to provide a stable surface with a similar impedance of the record, or so they say. Some think the best mats are forms of acrylic, methacrylate (Delrin), carbon, or vinyl. The trick is in preventing vibrations from reflecting back to the record. Achromat does this with bubbles somehow. Perhaps a lead sheet would be more affective.

Beside the obvious problem of weight, lead is soft and manufacturing a flat sheet might be a problem, but I doubt if any material is more affective at slowing vibrations. A lead sandwich or under mat might be ideal.
Regards,

Fleib,
To paraphrase Mike Tyson...

Everyone's got a theory until they're punched in the face

After listening to multiple different materials and combinations on the Victor DD turntables......I know what sounds best to me....and so far it's what the Victor engineers themselves agreed on, the pigskin thin platter mat.
The last mat I will try is the glass one....also designed for these decks.

The Walker Proscenium turntable uses a platter made of granulated lead and epoxy I believe...😎

The funny or sad fact is that the mat has a large effect on sonics,…. after all the money is spent on the tt, tonearm, and cartridge. It's the salt and pepper of vinyl.

........or have their ear bitten off. Bon appetit.

Sorry I chimed in.
This has already been done by Pierre Lurne, only with a platter rather than a mat. I happen to have some sheet lead. Might see if it's doable.