The “L” designator in e.g. Rimula R4 L stands for “Low Emissions.” What does this mean?
That the oil is a low-ash formulation so there is less ash in the exhaust, resulting from oil consumption. This means it prevents DPFs from blocking and potentially is more compatible with catalysts. When DPFs get blocked, the backpressure in the exhaust system increases. Which can trigger regeneration on some vehicles, but more importantly, it can impact fuel economy by 1-2%.
