Okay, I'll chime in here. I used to be in the fuel delivery business. I ran a tugboat that pushed a 145,000 barrel barge - that's a little over 6 million gallons. There are several different blends of diesel fuel depending on which refinery blends it. The premium diesel (also referred to in some areas as marine diesel) has additives added to boost both the cetane and the lubricity. Premium diesel came about due to the poor lubricity found in the new low sulfur blends. Seems there were some fuel pump issues with certain engines. Again, the base starts off the same more or less as everyone elses product, but the additives are added by each individual refinery. This is sometimes done at the refineries, and sometimes done at the tank.
This is what I've been told. I know the company where I work now, has a fleet of 17 vessels. There are two which we fill with 'premium' diesel and the rest get the regular stuff. Again, this is mainly a lubricity issue. We use millions of gallons a year, so I'm sure the owner is up to speed on the product. I doubt he'd toss away money for nothing. In fact, we have a regular fuel analysis program for each vessel to make sure what we get is up to our company's standards.
Doubt it makes a difference in a kubota. These are very high horsepower engines with an extreme duty cycle that see thousands of hours each year.
