A comprehensive explanation from the horse's mouth; in short it appears you can use 229.5 or 229.51 for your needs. If you don't have a DPF 229.5 will be a full SAPS and provide better cleaning and anti wear power over a 229.51 with a less robust additive package. All will be high HTHS:
Vehicles with the Mercedes Maintenance System starting with MY2005 can use 229.5 or 229.51 oils.
Vehicles with the Flexible Service System FSS from MY1998-2004 can use 229.5, 229.51 or 229.3 oils.
229.5 and 229.51 engine oils must be used with fleece oil filter when used with the Mercedes Maintenance System (MY2005+) in M112, M113, M272 and M273 engines. With FSS paper filters are fine.
MB sheet 229.1 approved oils
for passenger cars with gas and diesel engines, used to be minimum spec for latest (98+) engines, high detergent, dispersant spec suitable for normal drain intervals. Based on ACEA A3, B3. Note 229.1 oils are not recommended for MB's latest (2002+) 4 valve gas M271, M275, M285 and diesel OM646, OM647, OM648 engines.
MB sheet 229.3 approved oils
for passenger cars with gas and diesel engines with extended drain interval indicator FSS up to 20,000 km, or 40,000 km - 25,000 mi, current minimum spec for 1998+ MB engines, min. 1.0% fuel saving compared to 229.1, based on ACEA A3 B4. For gas engine of the M100 series, gas engines of the M200 series and diesel engines of the OM600 series (not models with Euro 4 diesel particle filters).
MB sheet 229.31 approved oils; LA "low ash" Oils
Mercedes pioneered this new spec for passenger cars with diesel engines with EURO 4 or Bluetec exhaust particle filters, e.g. W211 E200 CDI, E220 CDI. The spec was introduced 7/2003. They are called LA "low ash" or "low SAPS" oils, low on sulfated ash, phosphorus and sulphur to limit exhaust particle filter pollution. In 2004 the ACEA introduced the new C3 spec (mid SAPS, normal viscosity) based on it. Change intervals extend to 15,000 km.
MB sheet 229.5 approved oils; "MB Longlife Service Oils"
for passenger cars with gas and diesel engines with extended drain intervals beyond 229.3 oils, to 30,000 km, min 1.8% fuel saving, first oils introduced summer 2002. ACEA A3 B4. For gas engines of the M100 series, gas engines of the M200 series and diesel engines of the OM600 series (not models with Euro 4 diesel particle filters).
229.5 engine oils must be used with fleece oil filter designed for use with 229.5 engine oils.
MB sheet 229.51 approved oils; low ash long life
Mercedes pioneered this new spec for passenger cars with diesel engines with EURO 4 or Bluetec exhaust particle filters and longer service life than the 229.31 oils. The spec was introduced in 2005. Change intervals increased to 20,000 kilometers. Based on ACEA A3 B4 and C3."