State road tax on diesel is roughly .15-.25 cents a gallon so total tax is in the .40-.50 cents per gallon range for diesel.
Our State tax in Maine, on road diesel, is 31.2¢ per gallon as of July 2011.
Maine Fuel Taxes
The federal tax per gallon for road diesel is 24.4¢:
If we add 24.4 to 31.2 we get = 55.6¢ per gallon road taxes in the State of Maine for a gallon of diesel. Marina's selling off road fuel (which in Maine is ULSD) and heating oil dealers, do not pay this road tax and pay no tax on red dyed fuel. The only tax is a 5% sales tax which gets paid by the end user but not for home heating oil just off road fuel.. Thus they can potentially save 55.6¢ per gallon over the road stations per gallon price if their buying at the same price..
I was pretty close with "about .50". though a little low for Maine....
As far as the difference between marinas and convenience stores, marinas are usually much harder to get to and don't hold as much (smaller tanks). So it's generally cheaper overhead wise for a distributor to send a full 8500 gallon tanker load to a store than it is to send 1000 gallons on a smaller truck to marinas.
Depends upon the marina. My friend ran a large marina in NH and filled up sport fishing boats and mega yachts at a very good clip. These guys were filled at what I would have to guess is "transport" pricing. The boat I worked on could easily burn 400-500 gallons per day at about 120GPH and this was one of but 30 or so boats that ran to the fishing grounds regularly.. They were sometimes required to bring the tanker right to the marina forto fill some of the larger 100+ foot yachts. They used a huge "transport" type volume. Still the price charged per gallon to the customer, even in large volumes, was higher than the local road stations despite no state or federal taxes.
I can really only talk to what goes on in Maine and what I have personally seen. One day in 2010 I got behind the fuel delivery truck from our local fuel station which had just filled them up with ULSD. I followed it at 12 MPH the 1.2 miles to our local marina and then watched as the guy filled the marina tank. I specifically asked if this was ULSD or if he had another tank in the truck. "We add the dye at the tank farm in South Portland but use the same fuel as the road stations do, ULSD. There are multiple tanks in this truck.".. Neither station was getting diesel at "transport" pricing, our local station is a single entity mom & pop convenience store and gas with one diesel pump. Both of these fills could be considered "straight job" which is a slightly higher price than a full tanker "transport" pricing.. This same local station is the one where I noted the $1.25 difference between road and marina pricing...
Now it's not .50 per gallon cheaper,
When you subtract the ¢55.6 tax in Maine it can be less by that amount taking out any volume discounts.
and it's sure not $5.30 vs. $3.75 different, but it is more expensive for the marina than the store.
Those were actual local prices for marina diesel & road diesel from last summer. Not a joke.... Our local station was $3.75 and the marina $5.30 on the same day both of these locations are filled by the same distribution truck.. I remember it well because I needed about 30 gallons and considered jerry jugging it...
And convenience stores, etc. are not making 10% on a gallon of gas. Margin on fuel stays roughly the same regardless of the rise or fall of prices.
You are correct on that. That was my recollection from conversations with my friend Craig who owns a station in NH. I just called him and he told me he tries to make about 10-18¢ per gallon if local competition allows. This means that as the price goes up he makes less as a %. The last time we discussed this gas prices were much lower and the 10% number stuck in my head...
Still $3.75 vs. $5.30 with no road taxes is a large difference in net profit. That may certainly not be the case everywhere but in Maine it is a spread I have personally seen..