yes i have noticed that the omega does tend to produce mayo but luckily due to the design it collects up in the (removeable) filler neck so easy to clean out now and again. not helped with mine with short journeys but it has had gm oil in for the last 3 changes. be nice to know if other oils are better / worse in this matter .ive heard that castrol is bad ?.
mannol will be my next choice especialky at around £45 for 20l
The mayo also tends to form in the breather system as well. Hence needing to keep away from oils that are susceptible
That is what I found, too, frozen mayo in my breather system created much work when parked outside after short journies in -22 degrees Celcius, now changing cam cover seals.
How about Mobil Semisyn 10W40. Does that fulfil Omega V6 Y26SE spec, actually what the spec is? API SL?
https://www.mobil.com/en-fi/passenger-vehicle-lube/pds/gl-xx-mobil-super-2000-x1-10w-40