Typically Diesel as it leaves the refineries is virtually the same. The taxes vary on the road vs marine use diesel. For many years, road deiesl had greater taxes and so marine diesel was cheaper. In recent years that has changed. Diesel was dyed to distigusih marine from road diesel to demonstrate that the proper taxes were paid on the fuel in your tank.
Various outlets put biocides and conditioners in marine diesel fuels since it is recognized that marine diesel typically sits in the user''s tanks longer than road diesel.
Over the years I have gotten more water out of fuels purchased at gas stations than from fuel docks. I do try to fuel up a facilities likely to have a greater turn over in its fuel supply but I am not sure that I am not just being superstitious.
If I have concerns about the fuel that I am filling I first pump a gallon or two into milk jugs and let it sit a moment. Water and silt will separate out pretty quickly. The fuel should be translucent to lightly tinted. If in doubt you pour off a little from the top of the milk jug into a glass jar and look for debris. Anything you can''t see should be picked up by your filters.
Beyond the above, it is important to have primary and secondary filters, If you depend heavily on motoring, you should have a spare parallel filter/water separator that you can easily switch over to on the fly. I have a little rig that lets me reach the lowest point in my fuel tank and pump out any water or debris and I pump out enough fuel every time I do an oil change to determine the condition of the fuel in the tank.
Off road diesel is tinted with a dye to identify improper use in a road vehicle. Road vehicle distribution is tint less, off road is a pink die, In Canada off road/farm gas was dyed purple and would leave/ transfer to the gas tank walls. We used it in the lawn mowers, tractors etc..
There are grade 1 and grade 2 diesel fuels, #2 being the summer grade but is subject to gelling at cold temps, #1 is added to control the gel point. There is more energy in #2 being a heavier distillate. Cetane # for #1 is around 44 and #2 is around 40.
#2 and heating oil are both mid grade distillates of similar weight, heating oil does not have the additive packages that diesel does. Heating oil would have higher wear to the injector pump/ due to less lubricity.
If you are not sure of your supply use a Baja filter to help protect you from crud and water...
Jet fuel is really a slightly higher grade of diesel. We routinely take on fuel when we fly our helos off shore (oil platforms, rigs, ships) and the fuel is checked for contaminants and water. You can buy these testers I am sure for just a few bucks. It may save your life one day.
More than likely, the fuel dock is going to have the same stuff as the station up the street except with red dye. With the introduction of ULSD (ultra low sulfur diesel) in 2007, it got a little more complicated. ULSD was required at all shoreside stations because the diesel particulate filters on the engines cannot handle the sulfur but boat engines do not have these filters and only need LSD. For the most part, everything in the US has become ULSD but some fuel docks may still stock the strong stuff. The issues with ULSD are that it gels a bit earlier(not an issue except for the arctic explorer types of sailors), and it has a little less lubricity.
If you watch the big boats fuel up, they often have a home heating oil truck come which is essentially the same stuff as #2 except for additives. However, this will change soon due to taxing and environmental regs on the fuel.