This is a bit unfair imo. The work involved to get engines to a low emissions standpoint is massive, the advances made are huge. To do this actually requires you burn more fuel, if you run for more efficiency then you run hotter, you run hotter you increase your Nox levels. Which you can't do as the limits for the tiers are already in place. The new Ford models have an economy range, skinnier tyres, more fuel efficient engines. These have been noted as more noisy, worse response etc. If a manufacturer could get the extra 10mpg over the opposition, while retaining the noise, vibration, response levels demanded by the consumer then they would be all over it. It's what the engineers are striving for, they certainly aren't holding back through lack of effort. The use of EGR technology to drop emissions levels shows the massive leap needed for the targets to be met. You need to completely re-design the engine to meet new emissions levels. After treatment just wont cut it, which is why CAT America had to sell a large range of engines while paying fines due to not hitting these targets. I can't find a good graph to show how difficult these targets are to reach but if you imagine a square, You have Nox, CO and particulate emissions all needing to be in the confines of that square. Now for the next tier of emissions reduce the area of the square by 50%, that's the target you need to meet. It would be like asking someone with an engine that can do 50mpg to make one which now does 100mpg, it's an enormous task. Reduce fuel consumption, at one point in the load curve the emissions stray a tiny amount outside of this box, stop, back to the drawing board. Economy = Easy, Response and power = Easy, Noise and vibration = Easy, all 3 at once = Massively challenges! Vastly off topic but I have to stick up for my ex colleagues Dave!