I'm thinking about taking I-64 through Louisville and Lexington, then I-79 through West Virginia, followed by I-68 through Maryland. According to the internet, I-68 parallels I-70 through PA but has a more lanes, no tolls, and a 65mph speed limit.

http://www.roadstothefuture.com/I68_MD.html
That would add 78 miles and 38 minutes to my trip (one way). The fuel cost at 24mpg in my brother's Prelude would be an additional $13 (one way, $4.10/gal for premium). That's still cheaper than $18 in tolls.
It's a savings of only $10 round trip. The speed limits are higher, its an interesting new route I've never taken and there's less traffic congestion, but I'd be in the car for 40 minutes more.
Additionally, the slower route through PA could possibly mean higher fuel economy, which would nullify the $10 savings.
Is it worth it? Like last year, this would be a one-shot drive so we'd have to wake up, hop in the car, and go. I'd normally travel for three weeks on a trip like this, take the scenic route, and wander all over the east coast, but my brother wants to get home to study for the MCAT.


