Take I-95 to Bangor, exit 182 A (formerly exit 45A), continue on I-395 to exit 6A, and drive East on Rt. 1A to Ellsworth, then Rt. 3 to Bar Harbor.
Take I-95 to Augusta, exit 113 (formerly exit 30), and follow Rt. 3 to Bar Harbor
(A bit longer, but more scenic).