This is a simple choice - if you want your motor to last as long as it can, then use synthetic oil. Game, set, match.
Here's a good, basic video on synthetic oil: https://www.youtube.com/watch?v=ZivhWIM0Q8s
and be SURE to watch the cold weather "pour test" at apprimately :48 seconds into the clip.
Everyone would agree that the most damage to any motor occurs on startup, and synthetic oils will ALWAYS flow better to the moving parts on startup than ANY conventional oil, all things being equal (i.e., they're both the same grade - a.k.a. "weight"). When deciding on the oil you'd like to use, keep that thought in mind - how quickly will the oil get to the moving parts when the motor fires?
"More confusion occurs because people think in terms of the oil thinning when it gets hot. They think this thinning with heat is the problem with motor oil. It would be more correct to think that oil thickens when it cools to room temperature and THIS is the problem. In fact this is the problem. It is said that 90 percent of engine wear occurs at startup. If we are interested in engine longevity then we should concentrate our attention at reducing engine wear at startup." - http://www.bobistheoilguy.com/motor-oil-101/
"We left off discussing that a 0W-30 grade oil is not thinner than a 10W-30 oil. They both have the same thickness at operating temperature. The 0W-30 simply does not get as thick on cooling as the 10W-30. Both are still way to thick to lubricate an engine at startup."
"Now you can see that the difference between the desired thickness your engine requires ( = 10 ) is closest to the 0W-30 oil at startup. It is still too thick for normal operation. But it does not have far to go before it warms up and thins to the correct viscosity. Remember that most engine wear occurs at startup when the oil is too thick to lubricate properly. It cannot flow and therefore cannot lubricate. Most of the thick oil at startup actually goes through the bypass valve back to the engine oil sump and not into your engine oil ways. This is especially true when you really step on that gas pedal. You really need more lubrication and you actually get less." - http://www.bobistheoilguy.com/motor-oil-102/
Although much of this video refernces the cold environment of Canada, the concept is the same in warmer climates. Take a look at this video: https://www.youtube.com/watch?featur...&v=OWiQyR7PWII
and in particular, watch the demo at approimately 2:08 into the clip. I think it's an excellent demonstration of how a 0W-30 flows much better than a 5W-30, which flows much better than a 10W-30, etc., etc. At approximately 4:58 into the clip, you'll get an idea of how the grade of oil can impact the protection of your engine. I don't remember if they're referring to conventional oil or synthetic, but I'm guessing it's conventional. Keep in mind that synthetics flow better than conventional when they're cold, both when the ambient temperature is cold and the motor is cold.
Some people who watch the video might say, "Yeah but this doesn't apply to me because I live in a warm location...". I would argue where you live is irrelevant - your motor and the motor oil still cool off when the motor stops. The goal when the motor starts is the same - how quickly will the oil circulate to the moving parts to protect the motor?
If you want to learn more about oil and discuss them ad nauseam, join the forum at: http://www.bobistheoilguy.com/forums/
I'm not suggesting you use Mobil 1, but here's an interesting video of them pimping their oil: Mobil Million Mile BMW 325i - https://www.youtube.com/watch?v=gHmMlU8Q-V8