Depends where you live. The Sunoco in Leonardtown is usually pretty reasonably priced, but they don't have pay at the pump, you'll have to go inside. The Exxon in Leonardtown can sometimes be a few cents higher, but they have pay at the pump. There pumps cut off at a later rate than most others so it can throw off your mpg calculations. In La Plata the Hawthorne Shell is pretty good for diesel. The only problem I've had is that there fuel was gelling from the cold weather we've had for the last few weeks. In Waldorf I'll usually go to the Myer's Shell (Pika Dr. & Rt. 5), they have 10 cents off on Mondays. I don't get over to Calvert much, but I know they have a Shell there in Prince Frederick near the Safeway on Route 2.
Since this truck is diesel, I would recommend that you start running a fuel additive, such as Power Service. Why run an additive you say? In October of 2006 the U.S. Government made it mandatory for most diesel stations to start selling ULSD (Ultra Low Sulfur Diesel), because it has a lower sulfur content (15 ppm compared to 500 ppm of Low Sulfur Diesel, the previously offered fuel), hence it's cleaner burning characteristic. The problem with it though is that when they took all the sulfur out, it removed the natural lubrication properties that diesel fuel already had, similiar to when they removed the lead from gasoline. ULSD doesn't naturally lubricated the fuel system in diesel trucks anymore, and if your engine was designed to run on ULSD than you could run into problems. Being that yours is an 06' Duramax, which wasn't designed to run on ULSD, I would buy an additive and run it regularly. The other problem with ULSD is that removing the sulfur also raised the cloud point. By this I mean that the temperature at which ULSD starts to solidify (or gel), is higher (as in now ULSD starts to gel around 32 F compared to maybe the single digits with LSD). When diesel fuel gels it plugs fuel filters and fuel system and won't allow an engine to run. The additive drastically lowers this cloud point and will allow you to safely run your vehicle in cold weather and not worry about getting stuck on the road. Another benefit of an additive is that it protects against algae growing in the fuel tank, once again, just another lovely side effect of ULSD.
Here's Power Service's website,
Power Service Products, diesel fuel additives, prevent gelling, clean injectors, disperse water, boost cetane, reduce emissions, improve fuel economy. They have two regular additives to run. One is in a gray bottle which is for the summer months. It will increase your cetane rating (similar to octane in gasoline, the more the better), provide the necessary lubrication that your fuel system needs, and it also contains fuel stabilizers. The other one is in a white bottle, which is for the winter months. It contains an anti-gel formula that will keep your fuel from gelling. It also contains lubricity additives and fuel stabilizers. I've run both of those additives interchangeably in all 3 of my diesel vehicles since ULSD was introduced and haven't had any issues with any of the "side effects" of ULSD.
