The best thing i've used to remove tree sap is (believe it or not) ice. The wedge cubes work the best and no chemicals or scratches. Just rub the ice on the sticky sap for 45 seconds. It chills the sap and makes it hard then either use your nail or the edge of the ice wedge and pop those spots right off.

 

Hot water and amonia added

 

Rubbing alcohol!!!!

 

A couple of the replies are about 3 years to late.