Thanks to all. The website was informative, as well.
As usual, it makes sense, as I tell my two sons, "to know things."
I have a feeling that the battery application in my small, limited HP boat (with converted auto engine) will not make much difference. But, since there is only a small difference in the cost, why sweat it.
1991 350 SDL (200K and she ain't bent, yet)
former 2002 E320 4Matic Wagon - good car
former 1985 300 CD - great car
former 1981 300 TD - good car
former 1972 280 SEL - not so good car
a couple of those diesel Rabbits ...40-45 mpg