The Wrong Oil?(!)

Preface: I don't know much about cars (yet!)

Took my '99 V-6 to a quick lube place because I was in a hurry. I saw that the synthetic oils were "on special", so I thought - what the heck! I love this car! Time to give some love back. So I said yes to the synthetic for the first time.

Anyways, I get home and I read the invoice and it says they added 5w20. (Castrol). Anyways, I thought I remembered it was supposed to be 5w30, so I panicked. I double check my owner's manual and sure enough it says 5w30.

So, what have they done to my engine? Is this "okay" or "normal" to go to the lower weight oil because its synthetic? Or was this a mistake on their part?

Should I get another oil change immediately, or can I live with this for the next 3 months? If I live with it, should I "baby" my car? I know its only a V-6, but I love to put the pedal to the metal on my car.

Anyways, some stern advise (or reassurrances) from you fellas who are more in the know would be kindly appreciated.

Thanks for your time,

Justin
(Toronto, Canada)

Thanks for the reassurances guys.

The last poster's question is strange though: "Why do they say 5w30 for '99's, but my '01 says 5w20?"

Don't the '99 and '01 have the same engine? The exterior is practically the same. Interesting.