AFAIK, there has never been a professional technical paper published that has shown any wear advantage to synthetics... I have looked. Nada. there are a few that show better upper cylinder wear on straight SAE 30 ... But they are few years old. And that oil choice will not work for many folks due to winter temps ...
There are some motors that do not like synthetics. The 5.0 V8 in my Big Bronco is one. 216,000 on the clock and it will rattle your teeth on cold starts with synthetics. Put in a quality dino oil of the same range, and it's quiet and good to go.
My Saab 9-5 with 143,000 is starting to do the same and it's factory recommended for synthetics. So now it's running on Rotella T6 and seems fine (but it's in the shop for a TCS/ABS repair
).
Wife's XJ6 does not care at all. It's fine on anything that resembles good oil. 178,000 on the clock and flying past ODB II Smog tests (so you know the rings are holding up OK
).
Filters make a difference. I run mostly Fram TG, Ultra or Napa Gold. Not for media performance, but for anti-drain-back valve seal so the galleries are full on cold start. Makes a noticeable difference. They all filter well enough to keep the cruddy bits down to the microscopic level.
Dino, blend, or synthetic is more about owner feel good and maybe winter performance than anything else. Yes cleaning is important. But BG109 will do that as it gets added the last 1,000 miles before a change.
And I've moved to annual changes since the oils now days seem to hold up so well that it's not critical to hit a mileage figure one way or the other. Look at the folks on BITOG that are going 10,000 miles and getting good UOA's ...
I need to get under the cars and trucks to make sure something is not leaking or falling off more than change oil. But as long as it's up on the ramps, why not ... Oils cheap and it goes to the recycle bin so it's not "wasted"