aaronazevedo

All - I tend to vacillate back and forth between Audi and BMW. My Audi experience is an UrS6 5 cylinder (wonderful), A4 2.8 V6 (horrible), and 2 different cars a '10 A4 and a '12 Q5 both with the 2.0T in them. My BMWs have been a few M cars with in-line 6 cylinders (amazing), as well as an '07 328i (great), and currently a 740i sport with a 4.4 V8 (great).

Beakerz

The 2.0T is a great engine, but keep in mind there were some oil consumption issues with some of the earlier EA888 engines (I think around model years 2010 thru 2012 or something like that) due to bad piston rings. I think there were also some timing chain tensioner issues around the same years. Anything 2013 and up should be basically bulletproof at this point.

The 4.2 V8 also has some issues (timing chain/guides as you mentioned) as well as carbon build-up issues.

Personally, I think the torque delivery of the 2.0T engine is fantastic. That small turbo spools up with practically zero lag and provides full torque just slightly above idle RPM, holding that peak till the mid-4000 range. You actually get more low-end torque at a lower RPM out of the 2.0T compared to the V8. I've always said the 2.0T engine feels like a bigger engine than it is simply because of the torque it makes down low in the RPM range.

I also prefer manual transmissions over automatics of any variety, but that's just personal choice.

JD15

How old a car are you considering? The S4 has not had the 4.2L V8 since the B7 generation and the S5 only had it for the B8 generation through MY 2012. If you don't want a V6, the S4 and S5 should probably be off your radar and you should instead be looking at the S6 or S7 with the 4.0TT. You could also consider the B7 RS4 with the 4.2L if you are indeed looking for an older car. I know all of the 4.2s with DI had significant problems with carbon build-up and required frequent carbon cleans.

superswiss

Yeah, I think you gonna have to narrow it down a little more. The 4.2 V8 is essentially a family of engines. Each one different from the other.

The B7 S4 had a port injected 4.2 V8. The two biggest issues with this engine are the timing chain and scorched cylinder walls. I owned a 2007 S4 and sold it with around 80k miles. I didn't have either of the issues, but my biggest issue with it was oil consumption. It burned through about 1.5qt every 1000 miles and eventually started to burn 1qt every 500 miles at which point I replaced the valve covers and that brought it back to around 1qt every 1000 miles. I had a constant oil supply in my garage for regular top offs.

The B7 RS4 then came out with a very different 4.2 V8. This one was for the first time direct injected and it was a high-revving concept engine. Its redline was at 8250 rpm. Very different engine from a driving perspective. The power comes from the revs. Audi used the same engine, but with a dry sump oil pump for the R8 V8. Both of these have massive carbon build up issues. These were the first generation direct injection engines.

Following this and before carbon build up became a widly known issue, Audi came out with the B8 S5. It had a normal revving 4.2 V8 like the B7 S4, but this time also direct injected and it had the scorching cylinder walls and timing chain issues addressed as far as I know, but also suffers from massive carbon build up.

After that, Audi went to V6 engines in the S4/5, but developed an all new 4.2 V8 based on the R8's V10 for the B8 RS5. This engine was essentially a smaller version of the V10 with two fewer cylinders. Red line of 8500 rpm, peak torque at lower rpm and made more power. It's quite a different engine. It's also a direct injection engine, but Audi took steps to mitigate carbon build up. It's not completely eliminated, but not nearly the problem it was in the other 4.2 V8. I own a 2013 RS5 and did a carbon clean at 60k miles. It did make a difference, but the other direct injected 4.2s have much more carbon build up at 30k miles than my RS5 had at 60k miles.

The 2.0T has evolved over the generations as well, but I think it was always direct injected and the differences are not at the level of the different 4.2 V8s, but I'm not that familiar with the 2.0T. That engine never did it for me. It's a nice engine for the cars it is used in, and it is quite punchy for a 2.0 once it's on boost, but I generally dislike small turbo engines. The issue with them is the power difference between boost and no boost. These engines use relatively high boost to make the power, so the difference is very noticeable, even though boost comes on relatively low in the rpm range. I find this engine somewhat annoying to get going from a stop, especially if immediate power is needed in order to merge into heavy traffic.