As someone who has done too many miles over the years with never a issue and got into the board way too deep I've done quite a bit of UOAs in the same engine, same operation with different oils.
I've posted them here and everytime the conventional oils did just as good to better than syn in my motors. This includes engines that see 90% short trips to 95% highway.
When you post the UOAs that show the data, you get the following respones;
1. You can not trust a $20 UOA
2. Its because of your operation
3. Its because of your engine brand (Ford, Toyota, Chevy and Dodge are the brands I've posted)
Then as soon as their oil shows a good report, its the best oil in the world.
So, I've given up. I've spent more $$ in UOAs here than I've paid for oil in the last 20 years. I've been called "untruthful" even though I'm not here to sell anything or justify my $$ spent on oils.
So, bottom line for me who has run syn, conventional, normal and extended OCIs? Conventional oil for the recommended OCI per the manual.
If your manual states you NEED syn, excellent. Use it.
There is a difference between NEED and WANT.
But don't think that just because you use the "better" (not my opinion) oil that you will make the magic high mileage number.
Today's oils are excellent. (like Buster says, most conventional oils have some syn in them is correct) If we can get 200k plus on yesterdays oils, today it will NOT be the oil that caused a problem.
Take care, bill
PS: Also all of the reasons you see posted here on why they run syn (ie, smoother, better MPG, cooler running (one poster said his temps under the hood dropped..) I have not seen in a H4, V6, I4 or V8 of different brands in my or families use.