Before you ask - no, the irony does not escape me. The irony that Audi, whose parent brand VW managed to demonise diesel worldwide with its emissions rigging scandal, leading to a downturn in derv sales, is shifting much of its S-branded cars to TDI power. Even Doctor Strange wouldn’t have seen that one coming in 14 million futures.
When you think about it, though, it makes perfect sense, particularly for the S4. The lovely old burbly V8 is long gone, with the most recent version powered by a V6. It was less thirsty than the 4.2, but not by much. And just think about what buyers were getting for their fuel economy sacrifices - or more accurately, what they weren’t.
The 2.9-litre twin-turbo V6 used in the RS4 and RS5 is already lacking in terms of aural drama, but the 3.0-litre single-turbo unit? I’d go so far as calling it boring. It’s not a terrible engine, but it holds not one memorable attribute.
Then we have to think about the typical S4 buyer. A great deal of them, you’d think, aren’t going to be out-and-out petrolheads. The S4 is about surefooted all-weather ability rather than true driver engagement. Anyone wanting more than that would surely make the jump to something with an RS badge or go for something from BMW or Mercedes.
This is where the new S4 TDI comes in. It swaps the petrol engine for a turbodiesel V6 of the same size, supplemented by a 48-volt mild hybrid system. Developing 342bhp, power has dropped only slightly relative to the old unleaded lump (which is retained in markets outside of Europe), but torque is way up from 369lb ft to 516lb ft.
0-62mph happens in 4.8 seconds, and the top speed is 155mph. Despite this, it’ll do 45.5mpg combined, according to the new WLTP cycle. Shaping up rather nicely, don’t you think?
IRL, the new TDI engine makes much more of an impression than its petrol counterpart. Although it wakes up a little later than we’ve become accustomed to with other modern diesels - with the party kicking off properly at about 2500rpm - the mid-range kick it gives is tremendous. The eight-speed automatic gearbox swaps cogs fast and effectively, although the fact that it upshifts for you even in ‘manual’ mode is a little annoying.
The S4 feels much quicker than the old one, and with the mild-hybrid system powering an electric compressor, lag is effectively combated. When you’re not sticking your foot down, that same 48-volt setup recuperates energy to help extend the stop/start system. Win-win.
I’m even - and don’t hate me here - quite keen on the trick exhaust, which adds a fake, five-pot like burble. It’s heinous on many levels, but the result of those vibrating elements in the tailpipe is surprisingly pleasant.
Dynamically, it’s all as-per the pre-facelift car. The front end is decent, and body control is good - long gone are the days when faster Audi products were pointlessly firm. If you nail the throttle a little too early in the bend, you’ll feel a little bit of a push from the rear axle just as the opposite end starts to run out of traction. Like I said - surefooted all-weather ability.
The dramatic changes to the facelifted A4 aren’t limited to the mill under the bonnet, either. Much of the bodywork is new and quite handsome in an understated way, it must be said. The pre-update cabin was hard to pick fault with, but now, it’s a little posher and filled with more tech.
The dual haptic feedback touchscreen setup still doesn’t feel like the best solution, though - using it on the move never feels quite as intuitive as you’d like. The I-Drive system in the BMW 3-series is much better in this regard (tactile rotary controllers FTW), the downside being that the G30’s brand new cabin already looks dated compared to the A4’s.
Fiddly touchscreens aside, the S4 is a likeable car on every level. Far from ruining it, the diesel has given the S4 an appeal it’s never had and made it more interesting to drive in the process. As a petrolhead, I feel like I should miss the old one, but I really don’t.