OK let me clear up a few things:

-Most people don't realize this; but synthetic blend oil is around 10% synthetic, 90% dyno oil. You might as well just go all or none. Paying a price that is halfway in between dyno oil and synthetic oil, to only get 10% of the way there is a rip-off.

-Nothing bad is going to happen if you switch to synthetic. All that may happen is if your motor has some leaking issues, they will become more readily apparent with synthetic, because synthetic does a better job of getting in the cracks and gaps; this is one of its advantages, but it comes back to bite high milage motors in the butt sometimes. If you notice oil consumption or leaks after switching to synthetic, you can either keep using it and just live with it, or if it's bad enough, just switch back to dyno oil.
Or the best solution yet is just use a higher viscosity synthetic oil. In other words, if you were using 5w 30 dyno oil, just switch to 10w 40 synthetic oil and it'll help with leaks.

-IMO, and through all of the research I've done, Mobil 1 synthetic is the best oil out there. Some also say Royal Purple is good, but that's more expensive and hard to come by. Mobil 1 synthetic is a tad expensive too... it's anywhere from $18.88 for 5 quarts at some Walmart stores, to $5 per quart (so that's $25 for 5 quarts) retail price at most auto parts stores.

But considering you can go twice as long without changing a good synthetic oil, it pays for itself. Make sure you use a good filter as well, like a Honda OEM filter or Mobil 1... stay the heck away from Fram with their glued cardboard filter retainers and non-existant anti drain back valves.

If you want to learn more about oil and oil filters go to www.bobistheoilguy.com

I know, weird name, but extremely informative and unbiased site with forums, independant tests, etc.