Help with Oil

So I have the base RSX and I need new oil. I want to put synthetic in it and I have heard that AMSoil is the best, but there seems to be a big difference between the 5W-20 oil that my car supposedly needs and other oils. Basically the 5W-30 oil performs a lot better. SO what would happen if I put the 5W-30 oil in my car?

Honda engineers wouldnt have said to put 5W-20 in there if they didnt feel that was the best for your car... I would just get a 5W-20 synthetic and call it a day.

Amsoil is the best. Use their new 0w-20 oil it is recommended wherever a 5w-20 oil is recommended. http://www.synthetic-lubricants.com/100_synthetic_0w20_motor_oil.htm