Synthetic oil ?

Does anyone out there know anything about synthetic oil? I think I heard years ago that it is better for modern cars than natural oil. Any ideas?Synthetic oil ?
I first tried synthetic oil a number of years ago and noticed an instant difference in my car's performance. It has increased my gas mileage, but only insignificantly, with the greater advantage being that it better protects the car's engine from excessive wear. The cost is greater for an oil change, but the recommended distance between oil changes is greater for the brand that I use which is Amsoil - 15,000 miles between changes as opposed to 5,000 miles for the regular oil.Synthetic oil ?
Yes it is far better, better gas mileage, better pick up. I notice it big time after an oil change and I think changing oil in a car is one of the best things you can do to boost power and smoothness. However, there is one catch, you are supposed to use synthetic in a new car from day 1 otherwise you wont have prevented the damage caused from regular oil. In other words, if you have 60k on a car the damage is done. Having said that I use it in my 2003 Civic that has 130k on it and Trailblazer that has 40k on it just to prevent more wear and tear. If you do switch to synthetic they make engine oil flush that you should use before changing over to remove that sludge and conventional oil in the oil pan. I still change it at 3000 miles bc performance regardless of what they say will still drop off after 3000, at least in my Civic. It's worth the extra money to me. Like Tom said, NEVER go over 5000 miles regardless of synthetic or not. I use Mobil 1.
Here is the thing. You can go out and have a place change your oil using synthetic. You will pay a much higher price. All oils are at least semi-synthetic. Yes a 100% synthetic oil does not have the breakdown like conventional oil, but ';conventional'; oil is semi-synthetic. Don't waste your money on it.
It lasts a little bit longer before it breaks down. You might only have to change your oil every 5,000-10,000 miles with synthetic oil as opposed to the recommended 3,000 with traditional oil, although I would never suggest anybody go longer than 5,000 miles before an oil change.
synthetic oil is better for any engine old or new as long as it's not leaking oil or burning it.