Synthetic blend with the highest synthetic oil concentration?

In my opinion, for what it's worth, is a blend could have as little as 5% synthetic and
call itself a 'blend'. A blender can and likely has altered the percentage as market and price
Just buy the cheapest synthetic at Wally World or other big box store. The 3.8 isn't fussy
or hard on oil IIRC. I've had 5 of them over the years.

My 2¢
I've made my own blend, mixing about 1.25L of Synthetic 5W-40 with 3.75L of 20W-50 to get a 15W-50 blend, both oils from the same brand and product range so probably very similar add packs.
I would guess it's similar to the way they do medicines, no matter what brand it is, they all seem to have the same amount of active ingredient...
With blends now being almost as expensive as full syns, it may be less expensive to switch to full syn. Most, if not all, are good for double the OCI...
If you are seeking the highest concentration of synthetic oil, why not just go full synthetic? At $12 per jug, you could be buying Pennzoil Ultra Platinum using the current rebate.
Exactly. Or if you have over 100k mis def go w/ "high mileage full synthetic" oil. Many are quite reasonable in price! Valvoline or Pennzoil etc are very good. Motorcraft semi-synthetic even has rated very well on OCIs here last I checked ..& is pretty cheap @ walmart for 5qt jug!