I have an 81 SD and aEuro 86 500 Se though not the same car as the 560 they are similar. You sure are talking about two different cars even if they are both 126's.
My SD gets right around 28 MPG and has adequate acceleration but sure is not like the gasoline V8 .I get between 16 and 20 MPG with the SE, sure would drive them both. My SE though driven less than the SD cost at least twice as much in up keep and fuel...........
William Rogers.........