Motul 4100 SYN-nergy Spec 10W40 in 5 litres is a full oil change for most cars in one container, which is what makes it the sensible service-day buy. A 10W40 remains the workhorse grade for a large share of the vehicles on South African roads, particularly engines that have covered real distance and higher-mileage petrol and light diesel units, where a thinner grade can lift consumption or soften hot oil pressure. The 10W winter rating gives adequate cold-start flow while the 40 hot grade keeps a solid film once the engine is loaded. Confirm the manufacturer’s required performance specification and approvals alongside the viscosity, since some engines demand a particular approval rather than simply a 10W40.