Years ago in POrtsmouth, N.H. during one of the many historic fuel price spikes, prices at the fuel dock were about $1.50 higher than home heating oil/offroad diesel. Wasn't much of an issue for us, since we barely used 200gal a season
, but the boat that I helped out on during tuna season was a 41' Viking. Very fuel efficient boat at a burn rate of 22gal/hr running at 20knts. LOL The owner of that boat struck a deal with a heating oil company in Kittery Maine whereby they would bring a truck down to the town dock at a specific time and we'd fuel up there.
Not sure how long that continued, as we sold our boat and lost touch, but it was an interesting play, and save a lot of money filling up.