Originally Posted by qqq1970

I had an offer I can't resist but otherwise I'd have waited for the TDI. I drove diesels when I travelled in Europe and it is a sensible choice. Unlike hybrid, diesel is a mature and proven technology. While pick up from standstill is slower than the 3.0T, the TDI's low end torque is very handy in passing traffic. Most of us seldom drive to the redline so the nameplate peak 310 hp at 5500 rpm is irrelevant in most driving situations. If we look at 1500-2500 rpm used in normal driving situations, we harness an estimated 244-314 lb-ft of torque and 85-150 hp respectively from the 3.0T. For the 3.0TDI at same rev range, the full 428 lb-ft of torque is available and produces power between 105-180 hp respectively. So we get more useable power from TDI and better fuel economy than 3.0T in normal driving rev range.

In Europe 70% of cars sold is diesel and in UK the only gas A6 sold is the 2.0T hybrid, S6 and RS6 the rest is all diesel. Europe sells an A6 3.0T biturbo diesel that has 313 hp, a monstrous 479 lb-ft of torque that tops a Ferrari 599 and 0-62 mph that beats the 3.0T by 0.2s according to EU figures. The performance gap between gas and diesel is more apparent beyond 62 mph. Someone posts on YouTube a 3.0T takes 24s to hit 125 mph and 46s to hit 155 mph. A 3.0 biturbo diesel with only 3 hp advantage over 3.0T achieves that in 20s and 38s respectively because it beats 3.0T in hp across the rev range. It is no wonder the business case for gas engine in Europe is weak when it doesn't beat the diesel in performance nor mileage. Where I live, diesel costs the same as regular gas, so you get double benefits from better mileage and lower pump price.

Are there shortcomings in diesels? Yes there are a few. The heavier diesel engine means weight distribution is more biased towards the front at 59/41, compared to 55/45 for the 3.0T and there is more understeer. Upfront cost is higher (same in Europe) so it takes a couple of years to get the payback in fuel savings. If you intend to own the car long term diesels make a lot of sense, if you lease or own less than 4 years then diesel is not for you. Diesel crankcase is more sturdy to withstand the higher compression ratio and hence usually lasts longer than gas, but most of us don't own the car more than 15 years.

All that said, I think Audi TDI pricing is wrong. In Europe the 3.0TDI we get is the diesel counterpart to our 2.0T gas model so the $2,400 diesel premium should be over the 2.0T not 3.0T (alright, to be fair the 245 hp TDI performance is better than 2.0T so maybe another grand or two over 2.0T. Europe has another de-tuned 3.0TDI that generates 204 hp that is a real counterpart to the 2.0T). In Europe the 245 hp TDI is priced below 3.0T so don't know why it is the reverse here. Now if they bring the 3.0 biturbo TDI monster then it would make sense to tag a $2,400 premium over 3.0T. As it stands it is hard to convince customers to go with TDI that costs more than 3.0T but weaker performance, at least on paper. As I said above, practically the useable performance of TDI is not worse than 3.0T.

I look forward to the day when electric hybrid is tagged to diesel engines. That would be marriage in heaven.

Thanks for bearing with my long blurb.

Originally Posted by awktane

I'm not an owner, and therefore can't speak of the long term benefits. I have test driven all members of the entire *6 line a few times. If the choice were between an A6 and an A6 TDI there is no doubt in my mind that I'd go TDI.

I'm still in love with the S6 though obviously there is a huge gap in mileage. I never felt as though I was pushing the S6 with standard driving whereas with the A6 TDI the pedal hit the floor occasionally as I asked it to accelerate faster than it could. It's hard to say that without making me sound like a crazy driver... but perhaps others will understand the sensation.
There is huge and simply amazing torque off the start... but no follow through.

Originally Posted by awktane

I'm not an owner, and therefore can't speak of the long term benefits. I have test driven all members of the entire *6 line a few times. If the choice were between an A6 and an A6 TDI there is no doubt in my mind that I'd go TDI. My reasons match many of the others above. I could tell when the torque's benefit passed the peak and felt the lack of horsepower thereafter. I would also like to add the danger of the quiet engine - it removed some of the sensation of speed for me. I'm still in love with the S6 though obviously there is a huge gap in mileage. I never felt as though I was pushing the S6 with standard driving whereas with the A6 TDI the pedal hit the floor occasionally as I asked it to accelerate faster than it could. It's hard to say that without making me sound like a crazy driver... but perhaps others will understand the sensation. There is huge and simply amazing torque off the start... but no follow through.

Originally Posted by perlfather

comparing it to an S car is .. well not useful.

Originally Posted by in2dwww

The key with these modern diesels is to short-shift them in a way that you do not exceed the torque band.

Originally Posted by in2dwww

I've had a VW 2010 Jetta TDI and a 2013 Passat TDI. I now have a MB BlueTec and an A6 TDI on order. Once you go diesel, you never go back. My only regret was selling the Jetta TDI for an A4 gasser. The Passat was a regret because it was a badly made car. The MB is a locomotive.