Colour me surprised
This surprises me not a bit.
Several years ago I owned a Toyota, specifically an Auris D4D SR180 model. It had a 2.2L Turbo Diesel engine, using what Toyota claimed was "Clean Air Technology", and supposedly had the lowest NOX emissions of any available diesel. I think this was all true, as the fuel economy sucked massively.
It had about 170-180BHP, comparable to the more sporty VW Golf TDi models of the day. But the MPG of the Toyota was *way* below what the Golf produced. With reasonably restrained driving, I used to see 28-35Mpg from the Toyota. The comparable Golf I owned gave at least 10Mpg more. On the forums at the time there was a well liked tweak to improve MPG, which involved removing the EGR valve. Of course, the purpose of the EGR valve was to recirculate exhaust gases back into the engine, which removed excess oxygen leading to much lower NOX.
In other words...it seems to have long been the case that to make diesels "clean" in terms of NOX emissions, you can choose MPG or power, but not both. I think Toyota got so fed up at people moaning about poor MPG from their genuinely clean diesels that they gave up and have gone with hybrid technology instead.
Biting the hand that feeds IT
