[Landshark]

found this:

"Fuel consumption

All models do have 90 litres fuel capacity.
The 1989 500SEC I owned required (depending on my driving style) 13-16 litres unleaded 95-octane fuel.
The 1991 560SEC I own now requires between 14-18 litres. The Cruise Control ("Tempomat") of that latter SEC definitely aids saving fuel.

What S, SE, SD, SEL, SDL and SEC abbrevates
The model number indicates the engine type (e.g. "500" for the 5.0-litres V-8) followed by the tokens S , SD, SE, SDL, SEL or SEC.


S stands for "Sonderklasse" or "Special class".
SD stands for "S-Klasse Diesel". Diesels were only available in the USA.
SE stands for "S-Klasse Einspritzer". All SE models are sedans (4 doors). "Einspritzer" is german and means the car has a electronic fuel injection system.
L stands for "S-Klasse Einspritzer Langversion". The SDL and SEL models are sedans (4 doors). SEL models have a longer wheelbase (increased by 140mm) than their SD or SE counterparts, which make them more comfortable to drive.
SEC stands for "S-Klasse Einspritzer Coupé". All SEC models are coupés with 2 doors but 4 true seats and all have V-8 engines. There was no Diesel Coupé.

For example, the 280S was a sedan (4 doors) and applies a carbureter instead of an electronic fuel injection system.
The new V-6/V-8 Engines


Top speed of a 420SE/SEC is beyond 220 km/h. It develops 325 Nm. Fuel consumption: ~11.9 litres.
Top speed of a 500SE/SEL/SEC is beyond 230 km/h (acceleration 0-100km/h in 8.1 sec.). It develops 390 Nm. Fuel consumption: ~12.4 litres
Top speed of a 560SEL/SEC is beyond 250 km/h (acceleration 0-100km/h in 7.0 sec). The 5.6 litres V-8 develops 430 Nm. Fuel consumption: ~15.1 litres. The 5.6-litres V-8 is based on the 500 V-8; a special "ECE" version was available as an option that develops 300 PS.
If the V-8 engine is properly maintained it can easily run 400.000 kilometers without a rebuild. I've heard from SELs in germany that run more than 600.000 kilometers with their first engine. "