Q We frequently hear that the diesel engine is not so
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harmful to health as the petrol engine, but what is the difference in their relative emission levels? Does anyone have any figures?
In recent years there have Abeen several comparative tables published, some in CM. The most recent reference that we have seen was in the paper by Dr D. Croney and Mr L. H. Hall of the Transport and Road Research Laboratory, presented to a meeting of the Institution of Highway Engineers.
They pointed out that diesel engines emit 10 times as much smoke and particles as petrol engines, but only petrol engines emit lead particles in the exhaust. They used the following table to show not only the comparative pollution but also the very different levels of emission in different working circumstances. "Trace" indicates that a substance