In my opinion, you're actually better off purchasing a brand new 2011 Honda Civic LX instead of the '08 Civic LX with 36k miles on it. The newly designed '12 Civic will be out soon, causing great pricing on the "old" '11 Civics. In my market (Cleveland, OH), you can get an '11 Civic LX (with automatic transmission) brand new for $16,200 or less. That's only $2,700 more than the 3-year old Civic. If you want an even better deal, you should be able to snag a brand new '11 Civic LX from a Chicago-area dealer for $15,000 or so, bringing the difference down to only $1,500. If you have good credit, you can also get 0.9% financing through American Honda Finance (good through 5/2/11). This is a unique case where buying a new car is actually a better deal than buying a 3-year old used car.
Check out the Honda Civic Prices Paid forum on edmunds.com for more real-world pricing info on new '11 Civics.