Esters vs PAO

[m37charlie]

I'm NE of Moscow Russia, have driven 16K mi this summer. Alaska to Halifax, Antwerp to Mongolia, now returning to W Europe. I run Delvac 1 75W90 in diffs and portal hubs.
Yesterday I leaked 300ml out of 700 fron the inside (CV to portal) seal left front. I refilled 300 last night plus about 55ml today while running. I am refilling with Penrite Full Syn 75W90.
The last 2 checks over 140mi no leakage. The seal has no seepage.
I hypothesize the Penrite has a higher ester/PAO ratio and the seal has swelled shut. I of course have spare seals, 3 actually but it is quite a job going thru the disk brake, hub, gears and bearings to get to it. There is a MB shop in Moscow just for modern Mogs about 200mi away.
I may switch on my next change to highest ester Redline, it does have 90K mi on the truck.
Charlie

 

[4WD]

How old were the seals to start with ?
I run the Delvac syn - and lots of HD trucks and heavy equipment -
But, yeah can't go wrong with Redline (maybe harder to find than Mobil 1 etc) ...

 

[m37charlie]

10 yrs, 90k mi
Charlie

 

[Jetronic]

Do you keep a record about your travels online? Seems like a very interesting trip, would love to hear/read how it all went in practice.

If the penrite is working, stick with that, I suppose?

Look at Motul, they also use Ester based oils. PAO in itself shrinks seals, and is used extensively in synthetic gear oils. There's no way of knowing how much of an oil is ester or pao though. Even Redline uses a pao/ester blend.