I have a 2005 Honda Civic with 85K miles. Should I switch to synthetic oil?

You don't ever need synthetic oil in a Honda Civic, unless it's at owner's discretion. At 85k miles you should start thinking about maybe a higher mileage type of oil, especially with Honda's being known for burning oil.

not unless you want to double your oil change bill for no reason. If your car is running fine then keep the oil clean there are no advantages to a synthetic and the hype is not worth it. I tried it in several vehicles and after three years all I can say was I spent more money on oil changes. It got dirty like regular oil at about the same time as regular oil. The one problem I had was with a vehicle that used some oil when I first got it all that happened was it used more oil and when I went back to conventional oil things returned to what they were. The theory behind synthetic is that the oil molecules are smaller so more molecules equal more protection But if the oil acts the same as other oils and does not seem to do or change much of anything what are you paying for?

Why not? The drawback is expense for synthetic oil. However, do not mix synthetic with conventional oil.

Refrence your service manual, if you do not own one I would HIGHLY suggest you pick one up ASAP at Carboagez.com

And why would you want to do that? Gone racing somewhere real hot?