Dino versus syn oil and 3,000 mile changes are part of oil religions. You do or you don't believe. With the quality of today's oils, whatever you believe you will probably be fine as long as you choose a good grade oil and change regularly. Worst case change per oil manufacturer recommendation(EXCEPT if your are under warranty), which with a lot of the synthetics means extended drains and interim filter changes.
Personally I just change my synthetic at the car manufacturer "normal" intervals. The LS normal is 5,000 miles. The severe duty cycle which most of us actually fit, is 3,000 or so, but generally assumed to relate to dino or blends. Severe is stop and go, short trips dusty or hot conditions. Any of these is considered sever by the makers.
I have used Mobil 1 since 1980 in all my personal vehciles. I did go to a 15,000 mile interval a few times in the past, but the oil got that strange muddy rainbow color which bothered me. Maybe if I changed the filter at 7,500, but in my mind what's the point of the extended drain if you have to do half the work anyway? So like I said, now I just go with normal intervals. I do not go with 3,000 mile changes. Afterall, syn has got to buy me something in comparison to dino, right?
As far as 0Wxx oils, I don't care for them since my 2 experiences during winter in Portland Or. was that the oil had significantly more cold start valve clatter than my regular Mobil 1 5W30 syn. I suppose it makes sense if you live where the sun don't shine half the year. But then I never used any 0Wxx except Mobil 1 so can't compare.
I currently run 5W30 Mobil 1 in my 2004 LS V8, which is technically higher vis than the 5W20 blend recommended, but there was an interesting posting yesterday regading how Mobil 1 syn is effectively a heavy 5W20 rather than a typical 5W30. "Shake the can test" seems to bear this out for me. The posting also went into and why Ford went with the 5W20 blend to begin with, not just for mileage but as a side effect, sounds interesting.
An interesting side note on "proper" oil change intervals, the US Military has determined that oil change intervals based upon mileage, typically the 3,000 mile interval is essentially bs. So they are doing routine oil testing programs and extending the drain intervals. Interesting info can be found by searching for AOAP. I suppose if it is good for a Million dollar tank or aircraft, or even a lowly $100K truck, then they aren't really worried that the engines will wear out just because you don't follow the 3,000 mile religion.
My personal opinion is that the 3,000 mile change is way overkill considering how good oils are now, including dinos. The 3,000 mile change was created way back when oils couldn't last much longer, if even 3,000 miles. However, it is cheap overkill, so no harm. Although there is one strange note I read a month or so back claiming that metal wear is highest in the first few thousand miles of an oil change and then settles down after that. So the short changers may actually be changing just as their oil is getting good. Not sure if I believe it but it was from at least a semireputable source that had run several oil analysis and food for thought.
Good Luck,
Jim Henderson