Dilettanteque

Hi all, there may be a thread on this already, but i couldn't find anything specific. So here goes. Has anybody had the pleasure of A/B testing the S-Line A6 with each of these engines? What's has been the experience?

jdong

I actually did, but as a disclaimer, I've never owned a diesel car and do not have a bias one way or the other. I mainly prefer to have an environmentally friendly car that is compatible with my demands for having a sporty/high-performance car.

I did drive the A6 TDI / 3.0T / 2.0T several times. Main notes:

- In terms of general acceleration/thrust, the pecking order is 2.0T, 3.0 TDI, 3.0T.
- In terms of gas mileage, this is undoubtedly 3.0 TDI is the best by a wide margin, 2.0T is next, 3.0T comes a bit below
- The 3.0 TDI has a generally likable character -- torquey, decent city thrust once it spools up, etc. However, the turbo lag is noticeable, and its refinement (e.g. engine noise level) is noticeably worse than the two gas engines. If you don't mind the engine noise or you are used to diesels, that's fine. But as someone who's primarily driven quiet gasoline and hybrid vehicles, the noise level and vibration of the 3.0 TDI felt inappropriate for a $60k+ car, in my opinion.
- The 3.0T has a much much stronger highway (e.g. > 55mph) pull than the TDI. The TDI, once thrust builds, pulls really strong at low speeds thanks to the high torque. However, it almost sets you up for a letdown (if you're used to gas engine power curves) once you realize the low redline and the torque dying off past moderate speeds.

I think the 3.0 TDI is a fine choice and it was really hard deciding between the 3.0T and 3.0TDI. Ultimately I sacrificed the fuel economy of the 3.0 TDI for the amazingly responsive feeling and solid highway pull of the 3.0T.

ninjajack

I also drove both back to back and totally agree with your comments. I was tempted by the TDI until I did a rough payback on the premium for the TDI.
Due to the cost of diesel fuel here in PA, I would have to drive about 60K to make the upcharge for the TDI. Combine this with the superior higher speed and lower noise of the 3.0T, the decision was easy. Had Audi priced the diesel closer to the 3.0T, well perhaps the decision would be closer.

DennisMitchell

The OP asked for a comparison with the bi-turbo 3.0 TDI. That motor is not offered in the USA.

jdong

Oh, whoops, I assumed it was the same TDI we got here. Today I learned something

fEArmE

Lol..This is priceless. Good review though!

AudioBear

Not a perfect review! You have to drive a TDI differently than you drive a 3.0T and if you don't know that you will get the results you got. If driven the way a turbo diesel needs to be driven, there is no turbo lag and not much difference in pick-up--if any. If you don't catch it at the right spot, it can not only lag, it can stumble. But you get used to the different style required very quickly. If I were younger I would offer to show you just how quick the TDI can be, but I have gotten over that. I'll grant 3.0T does what it does without any effort. I guess when you are as old as I am there is not much difference in noise; the new diesels certainly don't sound like diesels used to sound. Both are great engines. I admit I was very seduced by the 3.0T but getting 10 mpg more for almost the same performance and having driven diesels for years, I went with the TDI. BTW, I never even calculated payback because I didn't buy a $65K+ car to save money. It's just a matter of preference.

If Audi would bring their bi-turbo diesels to the US they would be almost as fast as the S6 and they couldn't allow that. Europeans get a lot more choices than we do in the US. Maybe that will change when they are selling a half a million Audis a year in the US.

jdong

I personally don't agree with the argument of needing to "drive it correctly" so you don't catch the turbo with its pants down. That's one of the big plusses of having the 3.0T with plenty of power throughout the range and instant supercharged response.

I think what you're saying is that with adequate anticipation (e.g. kicking down a few gears, moving tiptronic into S mode, etc) you can bring it into the instant torque band. The same arguments to a lesser degree applied to the 2.0T too, which has pretty bad torque response too when the engine down is at the fuel efficient cruising speeds that the ZF 8spd likes to maintain.

I might not be old yet but I'm not a speed freak either. I never said that the TDI is unacceptable or that the lag is bothersome. I just pointed out the difference in how the two cars feel back to back. I'm sure, as you said, given enough time with the car I can figure out how to coax the TDI to do what I want. Just like how with the 2011 A4's and the 8spd slamming into gear in stop and go traffic, there was a specific driving technique that minimized it. But that doesn't make the underlying difference go away. TDI or 3.0T, they're both great cars.


P.S. It's not like Audi is being mean about not bringing the 3.0 biturbo to the US. The EU has much more lax emissions requirements when it comes to smog. The 3.0 biturbo is an EU 5 engine, which has NOx emissions requirements of 0.18g/km (which is 0.29g/mi). In the US, that doesn't even meet LEV I emissions standards, which even an Escalade meets.

To put into perspective, LEV II ULEV's max NOx emissions is 0.05g/mi, which is what the 3.0T meets.

Diesels may be great at gas mileage, but they still have some ways to go for fuel economy. Audi says that the 2.0 TDI Ultra will meet Euro 6 emissions, which is a bit closer to what the US considers LEV II.