Audi A4 3.0 TDI quattro
What's six grand when you're spending 23? Well, it's 27.16 per cent, but let's not get too picky about it. At the risk of sounding like an Audi salesman, you need to find six grand if you have a choice between a four-cylinder Audi A4 2.0 TDI and the amazing V6 3.0 TDI you see here, because that's the difference: £23,200 plays £29,500.

Find it. Find that six kay, no matter what it takes: a second job,I don't know. Sell flowers at traffic lights. Do some mascot work at your local football club. Be inside that Golf Sale sign. Whatever. Just do it, own it, own this 3.0 TDI.

Somewhere in Stuttgart, or wherever it is, Audi has its engine development department, a team of people who are probably a lot more intelligent than you and I, beavering away, designing the next generation of Audi diesel engines to be better than they are now.

You can bet your house that these future powerplants will indeed be better. Smoother, more powerful, torquier, quieter, more efficient, superior in every way. For now, though, we're lumped with units like this 3.0 V6 TDI. And this is one of the greatest diesel engines in the world. Smooth, incredibly torquey, virtually silent. Look at that 0-62mph time: 6.1secs! Damn it, maybe it is the greatest diesel. BMW might take issue with the 'the' bit and, yep, their argument is solid, but it's line-ball.

So you're convinced, you're spending the extra six grand because it's worth it. Good. Now spend another £600 on 18in wheels while you're at it. The car looks a lot better on them than the standard 17s. And it's a real looker - far more purposeful and sleek than the old A4. And blow £1,100 on adaptive cruise because it's cool. Hmm, getting pricey at £31,200, but hey, you'll earn it back. I'm enjoying spending your money.

Now you've now got one of the best saloon cars on the road. A size bigger than its rivals from Mercedes and BMW, and with a trendier brand image. The chassis isn't perfect - the ride's a bit crashy - but we'll forgive it that. The engine makes up for it. £6k. A snip.

Words by Bill Thomas<ul><li><a href="http://www.topgear.com/drives/A2/A4/roadtests/10/01.html">http://www.topgear.com/drives/A2/A4/roadtests/10/01.html</a</li></ul>

"The chassis isn't perfect - the ride's a bit crashy - but we'll forgive it that."

Wonder what that will translate to when it gets to these shores. For simple comparison, if it were 1:1 and it was $6k more for a diesel motor in my A4, I would have to tell them they can keep it.

At one time that was about the price of going to a diesel on the Ford Super Duty trucks. Someone had figured out that the return on investment (in terms of the better gas mileage, etc) was somewhere out around 300-350,000 miles. Some truck owners will keep their truck that long, but I highly doubt the vast majority of Audi owners will.

The 3.0 TDI in the A4 won't be an efficiency/economy sale, it'll be the highest performance option available. And if the upcharge from the 2.0T to the 3.2 is $4500 then the beastly 3.0TDI would be a bargain at $6000. I just hope it's not $12,000 more.

First, remember us enthusiasts are a very small percentage of their new car sales numbers.

By and large the US market is not at all interested in a diesel as the high performance option. Diesel means high fuel economy. Why do you think VW for years has hardly been able to keep them on the lot?

Last month Mini was the highest gaining (of only 4 total makes to actully gain) in sales at something like 28%. Hummer was a miserable FAIL at something like -58%. The market today by and large first wants fuel economy in their daily drivers. Drivers looking for high performance will be looking at the S4 and S5 instead of an A4 diesel, given that it sounds like they will be close in price.

To me that's compelling and I think it would offer something that's not available elsewhere in the segment, at least until BMW brings their similarly high-power diesels over. If AOA had their wits about them they'd be leaning hard on the complete sack slapping that Audi diesels have been handing out in endurance racing to draw the line between high performance and diesel motors with the added bonus of good fuel economy.

Diesel will hit $5/gal this summer. That's just about a 100% guarantee. What kind of economy will it have to get to be more cost efficient than the V8?

The 2008 S4 pulls 13/20 mpg in city/highway according to Edmunds. Say gas is at $4.00 a gallon and diesel is at $5.00 a gallon.

I drive about 20,000 miles per year, so the yearly fuel consumption for an S4 would be somewhere around 1000 gallons assuming all highway driving. That's $4000 (NUT PUNCH!)

The 3.0TDI is supposed to get about 30-32 mpg IIRC, so it's yearly fuel consumption would be 667 gallons of diesel for a yearly cost of $3335. The yearly savings work out to about $665 or so in this simplified case.

The unknown here is what the diesel would/will cost compared to the V8, though since the V8 is only available in the S4 that puts it into the $48K neighborhood already. Hopefully AoA has enough damn sense to never price an A4 that high, but even if they do the diesel would win out on TCO from the very beginning despite the higher costs of fuel.

Another way to look at it is, "how high would the price of diesel need to be for the V8 to be cheaper to operate?" That we can arrive it much easier. If diesel went to $6 a gallon and gas remained at $4 then the V8 would make sense from an economy standpoint, but given that the price of gas and diesel aren't entirely independent since they're underpinned by the same commodity pricing for the raw material I don't think you'll ever see a 50% disparity in the price of the two.