The question is if synthetic oil is worth the extra money. If you don't put synthetics to good use you're wasting your money. In general, synthetics have a few characteristics that make them superior to conventional oils. Here's a quick list:
(1) Handle extremely high temperatures better. This means that if you have a cooling failure your motor should run a little longer before damage happens.
(2) Many synthetics have a natural multi-viscosity property that allows the blend to have less viscosity improvers (VIIs). The VIIs get mechanically broken down and cause your oil to thin out. Obviously, less VIIs means that this effect is less.
(3) Synthetics are much better at keeping your engine clean. I believe they require less of a detergent package to obtain the same result.
(4) Slightly less wear.
(5) Better fuel mileage in theory.
This isn't everything, but to summarize, synthetics tend to keep your engine cleaner and break down less from use. This means that you can run them longer than a conventional oil, but unless you run them long enough to offset the cost you really have not gained anything. Conventional oils are more than adequate to provide excellent protection in almost any engine for 5,000 mile.
I run my Sequoia 10,000+ miles on an oil change, but I use a carefully chosen oil (Castrol Syntec 0w-30 European Blend) that is spec'd as a long drain oil. I'm planning to switch to Mobil 1 Extended Performance because it's easier and cheaper to get and has been shown to go over 20,000 miles in an identical rig and still have some life left.
For the average user that isn't interested in testing their oil or pushing any limits, I would suggest running a name brand conventional oil for 5-6,000 miles and match it with your tire rotations. If you want to step up to the next oil Pennzoil Platinum is a great product for the price and should last at last 7,5000 miles in just about any application.
If your driving is extremely short trips this is harder on your oil, but if you spend any time on the highway at operating temperatures thing only get better when it comes to oil.
What kind of car do you drive?
Been there. Done that. Got the YNAB T-shirt!