We always use I-84 and always stop at Port Jervis on the PA-NJ-NY border at the Delaware River. Although that NJ fuel was the steepest on this long road trip, it was still way less than the rest of New England this autumn.
We had been in the habit of stopping at a Lukoil at that exit that has easy truck/bus access, and that has been competitive in price, but it changed hands recently and is now some other more expensive brand.
As you point out, there were several other Port Jervis stations that were cheaper, and next time we'll hit one of those.
Mike in GA
Yeah, I made four trips (4-wheeler - diesel) NC north (NY, Quebec, New England ..) July through early September and I saw those fluctuations at Port Jervis, too. Despite all the talk about the upheaval in Egypt and revolution in Syria pushing up speculation on crude oil in the Middle East, supply and demand has pushed gasoline prices way down in the past 6 months or so. Diesel prices haven't followed - partly because it's a cash cow for petroleum companies (and retailers), they can export it a high prices, and the price can be passed on "invisibly" to consumers. It's like it's set up to be good for everybody -- except real, individual people.
Oh, well, it isn't like the money I didn't spend on diesel fuel will do me any good after I'm dead.