Try this test for yourself. Get a quart of regular motor oil and a quart of synthetic oil. Put both in the freezer for 24 hours. Take the tops off and turn both up side down, and you will see a tramendous difference. The synthetic pours right out while the regular motor oil barely moves.
The only bad experience I have had with it was on a high milage car I had was using about a quart of regular motor oil once every two months. When I switched over to the synthetic I started using oil at twice that rate so I went back to the regular motor oil in that case because I couldn't afford to keep putting synthetic oil in the car at $4.50 quart.