Why do emission regulations impact lubricants?
There is no engine test that measures emission system stability, but the OEM’s have data showing that sulfur and phosphorus are poisons for catalytic converters and must be limited. Thus, in GF-4 oils sulfur is limited to 0.5%, maximum, in 0W- and 5W- engine oils and 0.7%, maximum in 10W- engine oils. Phosphorus is limited to 0.08%. This restricts the amount of zinc dialkyldithiophosphate, the workhorse anti-oxidant and anti-wear agent, which can be used in engine oils, which in turn, may restrict the amount of Group I oil in GF-4 blends.
