I have just read the What Car post and spotted this interesting statement:
"The gap between the official economy of the Audi A3 1.4 TSI 122 and 1.6 TDI 105 is 20.0mpg, but our tests show the difference is only 11.6mpg in real-world driving. What’s more, while the 2.0 TDI 150 version of the same car is less efficient than the 1.6 TDI on paper, it achieved an identical True MPG result of 54.1mpg."
Looks like that 2.0 TDI has the infamous VW Cheat code loaded!
That's just one test, depending on what kind of journies you make, you might get different results with an even bigger, or smaller petrol/diesel gap. Even 11.6 MPG will still make you £340 a year better off, then consider the fact that the road tax will be cheaper, possibly free on the TDI too. I've always thought when considering similarly sized engines, the more powerful one is also usually the most efficient too, especially when driving economically, more power = less down changing when going up hills/overtaking etc etc.
The only petrol units I would consider at the moment are either Ford's 1.0 litre ecoboost with 140 bhp, or VW's 1.4 with the same power, but with the ability to shut half the engine down.
My comment is more around the comparison of the 1.6TDI and the 2.0TDI where the 2.0TDI is less efficient on paper (EU Test with the VW Cheat running!) but in the real world matches the 1.6TDI (No VW Cheat running = better MPG but much higher NOX emmissions).
I think Diesels are going to get too complex in order to meet the emissions legislation, and that complexity is going to lead to expensive repairs when the cars get to 8-10 years old. These repairs will not be cost effective compared to the value of the car, this will lead to owners either removing defective DPF's for example, or the cars get scrapped early, either way the benefits of the emission controls are wiped out, either because they no longer exist on the car, or the car is scrapped early, requiring another car to be built. This last bit is obviously good for manufacturers though.
A friend of mine has one of the early Honda 2.2 Diesels, I think it has about 60K miles on it, it's now used as a fantastic garden ornament as it requires 4 new injectors (about €400 each), Timing belt and new DMF. I think total cost would be around €3k, but that would only get him another 50K miles when all of that would need to be done again. I admit this is an early Honda Diesel and hopefully they are much better now.
Basically, you need to be careful when buying a Diesel now, if you do a lot of town, short journeys you could end up in trouble. If you do a lot of Long Motorway trips, then Diesel would be a good choice. I don't think dealers are making this as clear as they should be though.
To be fair, that's just one example, in the grand scheme of things, Hondas are reliable and there are plenty of examples for sale with 140,000 to 160,000 miles on Autotrader of the same 2.2 diesel.
The biggest problem with diesels is the location. As you say, the emissions and emission related equipment only proves a problem in crowded city areas, diesels are more suited to longer journeys. You could say the same about electric cars, utterly useless for anything other that short urban trips. Or small petrol cars, hopelessly inefficient when revving highly on the highway. The government needs to enforce some kind geographical law, where people are encouraged to buy the kind of car that suits where they live and the kind of journeys they do. Crowded city commuters should buy electric or hybrid, those on a budget should buy small petrol cars, and those who do a lot of miles or live rural where everyday conveniences are further away than average should buy diesels.
It's not always true that gasoline (petrol) cars suck on the highway. Although most hypermilers are able to eke out more substantial gains off of the higher-speed, limited-access roads, I am consistently able to still get the best MPG on steady, mid- to high-speed journeys, both in raw MPG and in terms of % above rated fuel economy. That effect is really magnified when I have to use a/c (family on board, or that time I picked up the birthday cake).
Having said that, I do have an autotragic transmission, where torque converter lockup is a factor. I could use an extra highway ratio, taking the revs down 200-400rpm at freeway speeds (it revs at 2450/mi in top gear with lockup, which would be 38mph or faster) would be a boon. The car is light enough that responsiveness would still be adequate.