MB229.52 has a slightly better resistance to oxidative thickening than the 229.51 spec. For a 2010, unless you run fuel with a biodiesel blended in (like over 2%) or are extending your drain intervals, the 229.51 is fine. When we had a Benz diesel in the fleet (OM642 in a $printer) we got better results with the Valvoline 229.51 approved oil than with the Mobil 229.51...specifically it held up better as far as oxidation was concerned and the Mobil always burned 2 qts between services. At the time, we had no access to any Castrol MB approved product.
HDEO in Diesel Engines. No spark plugs here.