Motul Classic 20W-50 is the heavier oil in the classic range, and 20W50 is the grade most older performance and classic engines were specified around. The point of the formulation is the fortified zinc and phosphorus content, which forms the sacrificial anti-wear film that flat-tappet camshafts and high-lift cams depend on, since the lifter slides across the lobe rather than rolling. The heavy hot grade also suits the wider clearances and older gasket and seal materials of that era, and holds oil pressure in engines that have covered distance. The 2 litre bottle lets you make up an odd sump capacity accurately. As with any high-zinc oil, keep it out of vehicles fitted with a catalytic converter.