While test driving the 2010 Audi A3 TDI for this review, we showed it to friends and relatives, highlighting the fact that it gets about 40 mpg fuel economy. Inevitably, they asked us "Why aren't we all driving diesels?"
Being too close to the subject matter, we recited the history of diesel cars in the U.S., emissions regulations, and how the recession caused some automakers to pull back on their diesel plans. Five minutes into our lecture, our subject would go glassy eyed and comment on how the A3 looks like a really nice car.
Although the A3 is at the bottom of Audi's model lineup, it holds up Audi's premium car reputation with an overall look of quality and good materials. It really is a nice little car. However, being at the bottom of the lineup, Audi hasn't kept its cabin electronics up with the latest from the company, opting for what looks like the first generation of Audi's Multimedia Interface, with a DVD-based navigation system and interface controls mounted next to the LCD.
Although the body and interior appointments of the A3 TDI are no different from the gasoline-powered A3, you will notice a difference as soon as you fire up the engine. The A3 TDI's turbocharged 2-liter four-cylinder-diesel engine makes a harsh, rattling noise at idle, but the cabin is mostly insulated from this noise and quiet. Likewise, a lightly sulfurous odor emanates from the exhaust, but doesn't invade the cabin.
Checking the car's specs, we noted that the only gearbox available is Audi's six-speed, dual-clutch, automated-manual transmission--S-tronic in Audi nomenclature.
In just about every car we review, one of the first things we do is stomp on the gas to see what will happen. With the Audi TDI, we, of course, had to mash the diesel, and the result was not the tire-smoking fury for which we hoped. Instead, the car hesitated a bit, exhibiting a combination of turbo and diesel lag, before creeping forward.
But those first tentative steps quickly developed into a gallop as the engine revved up to 1,750rpm, where the peak torque of 236 pound-feet gave the front wheels the full twist they needed to move the little A3. From there, we could feel the linear torque curve carry the car irresistibly forward.
Diesels are a little weird compared with gasoline engines, favoring torque over horsepower. The A3 TDI only has 140 horsepower, and that only peaks at 4,200rpm. But the engine redlines at 4,500rpm, which doesn't give a whole lot of room to play. That peak torque, although strong at 236 pound-feet, only runs from 1,750rpm to 2,500rpm.
The Audi's dual-clutch transmission didn't always feel comfortable handling the odd power characteristics of this engine. First, it needs to shift gears much more frequently than with a gasoline engine, as the redline is so low. A couple of times while driving in typical urban congestion with the transmission in its Sport mode, we felt ugly thumps as the transmission downshifted abruptly, possibly confused by the low speeds and frequent stops.
Putting the transmission in manual mode, we threw the A3 TDI over mountain roads, braking and downshifting before each turn, then powering out. However, that low redline made manual shifting difficult, as we had to click the steering wheel paddles quickly to catch the gear change before the tach needle hit the ever threatening redline. Where a gasoline engine car would be quite comfortable coming out of a corner in third gear, we were in fourth, with a quick follow-up to fifth on the ensuing straight.
We settled on leaving the transmission in Sport mode for the fun roads, and standard Drive mode for urban and freeway driving. Under these circumstances, we couldn't complain at all about the car. In Drive on the freeway, traveling at 65 mph or 70 mph, the A3 TDI still had plenty of boost to pass other cars or climb hills. In urban driving it ran smooth, although we could have hoped for a little more initial boost for quick merges and the like.
Driving hard in Sport mode, the Audi's engine and transmission played well together, giving the little A3 TDI the right amount of power coming into and out of turns. The A3 itself is perfectly good for this type of driving, exhibiting very good handling characteristics.
Of course, what will attract most people to the A3 TDI is the incredible fuel economy. During hard sport driving, the trip computer settled in with a 32 mpg average, but it shot way up into the mid-40s during steady freeway and highway driving. In heavy traffic, we watched the mpg average drop to the mid-20s, something that might be ameliorated if Audi adopted the start-stop technology that's beginning to catch on with other automakers.