Diesel engines encompass the Auris range. The top-performing model, the T180, comes with a very strong 175bhp 2.2-litre unit, and there's a two-litre version in the middle of the line-up. And down at the bottom there's the 1.4-litre diesel fitted to the D-4D 90 tested here.This is the smallest (1364cc) and least powerful (89bhp) engine that Toyota fits to any Auris, but the D-4D 90 in its various forms is more expensive than the equivalent 1.4- and 1.6-litre petrol models. Although that might not sound like much of a deal, there's payback in the fact that the diesel is in a different league when it comes to economy, with an official combined figure of 56.5mpg.And it's not slow. In fact, it's a bit perkier than the slightly more powerful 96bhp 1.4 petrol. Why? Because those are maximum power figures; the diesel may lose out slightly at the top end, but it's a lot stronger at the engine speeds most people will use in normal driving.Similarly, on paper the D-4D 90 is slower than the 1.6 petrol, but it doesn't feel like it. I speak from considerable experience here, since I'm putting a 1.6 through a long-term test, and subjectively there really doesn't seem to be much in it.Despite all of the above, now that there's only one Auris in the office car park I can't help being slightly pleased that it's the diesel that left first. One thing I like about the 1.6 petrol is that it's pretty quiet most of the time, but that definitely doesn't apply to the D-4D 90, which is surprisingly noisy considering it has such a small engine for the size of the car.The noise never really goes away, even on motorways. That's partly because, unlike the larger diesels in the range, this one is fitted with a five- rather than a six-speed gearbox. I suppose the theory is that a 1.4 would have difficulty pulling a really long top gear, but I'd have liked to be able to slip into sixth occasionally, if only to cut down some of the racket.Also - and not to be too anoraky about this - the extra weight of the engine makes the front end feel more ponderous than that of the petrol version. The difference isn't great, and I don't imagine anyone would buy a mid-range Auris for the driving experience in any case, but I do reckon that the diesel is slightly (but perhaps importantly) more laborious to operate.The luggage volume stats for the Auris are 354 litres with the rear seats up and 761 litres with them down. In the latter format the luggage compartment length is just over 1.7 metres, which I've found to be pretty useful in the past.But thinking about putting things into the back of the car reminds me that the Auris also has what has become a very common design fault nowadays. Yes, we're back to the rear visibility issue here. There is an awful lot of metal and not nearly enough glass area, leading to the usual effect that it's ridiculously hard to see behind you in situations where that's important, such as reversing in a car park with lots of things (including children) to hit.This is par for the course with small and medium-sized hatchbacks these days, but Toyota has also added some new things to puzzle over. Every Auris comes with a range of features which, shall we say, must have seemed like a good idea at the time. There's the orange light in the centre console which relentlessly informs you that the passenger side airbag is switched on. There's the way the console itself arcs down from the dash in such a way that the oddments tray underneath it is very difficult to reach.There's the pair of lights on the instrument panel which tell you either to shift up or to shift down, often at times when doing so would be quite inappropriate. And there's the way the conventional button at the end of the handbrake lever has been replaced by a little slider on top of it.I can't see the point of this. The action required to operate it is slightly awkward, and although you quickly get used to it, why should anyone be asked to get used to something that's less comfortable - and no more efficient - than the thing it has replaced?Like our long-term car, the one tested here was in T3 specification - the middle one in the range if you don't count the high-performance T180. The extra £1000 over the list price of the T2 buys you heated door mirrors, six speakers for the audio system instead of just four, audio controls on the steering wheel, leather on the steering wheel and gearknob, electric rear windows and 16" alloy wheels rather than 15" steel ones.Other than by dipping into the options list, you can't go any higher than this with the D-4D 90. There's a T Spirit trim level, but it applies only to the 1.6 petrol and the two-litre D-4D 130 and not to the smaller diesel.It's difficult to become excited about the Auris, because despite several good points (and a few niggling ones) it's a rather forgettable car. Mind you, Toyota's talent with forgettable cars has led to it becoming one of the most successful manufacturers on the planet, and I dare say that the Auris will continue where several decades' worth of Corollas left off. Engine 1364cc, 4 cylinders Power 89bhp Transmission 5-speed manual Fuel/CO2 56.5mpg / 132g/km Acceleration 0-62mph: 12.0 seconds Top speed 109mph Price £14,600 Details correct at publication date