If you’re looking for a luxury performance vehicle, the Mercedes C43 AMG and Audi S4 are two of the best premium options available. Coming in right around a similar $60k price tag it is a close match between the two on which is the better performance sedan. While the Mercedes badge might carry a little more prestige, the Audi S-line has been a pinnacle of German performance for the last decade.
This article is going to cover the C43 AMG vs the S4 in terms of performance, reliability, and price. We are going to factor in not only performance from the factory but also performance and modification potential. We are mostly going to focus on the newer B9 S4’s and the brand new W206 C43, which replaced the W205 for model year 2023.
C43 AMG vs Audi S4 Stock Performance
Mercedes shifted directions slightly on the new W206 C43, changing from the previous 3.0L V6 twin-turbo, to a smaller 2.0L I4 combined with an electric starter system. The new M139 engine features the first ever electric turbocharger which actually results in a power boost over the previous larger engine. The M139 produces 402hp and 369lb-ft. of torque which is good enough to get the heavy C43 from 0-60mph in just 4.6 seconds with the 4Matic all-wheel drive configuration.
Audi stuck with the 3.0L turbocharged V6 TFSI engine in their S4. Despite the larger engine it actually underproduces compared to the Mercedes, at 349hp and 369lb-ft. of torque. It also has an all-wheel drive configuration but opts for an 8-speed transmission vs a 9-speed in the C43. While the power numbers might look a bit uninteresting compared to the 402hp from the C43 AMG, the S4 is actually 0.2 seconds better from 0-60mp, clocking a 4.4 second time.
The difference in 0-60mph times is likely due to weight. The Audi S4 is approximately 3,850lbs. whereas the C43 sedan is about 4,100lbs. making a difference of 250 pounds. Ultimately, the two are very comparable in terms of stock performance, albeit we do agree that the S4 seems to be a bit underpowered from a horsepower and torque output perspective. With that being said, since both engines are turbocharged there should be decent performance potential via aftermarket modifications.
Audi S4 Power Potential
The biggest benefit to the S4 is that it is using the same engine that the B9’s have been using since 2017, which means there is already adequate aftermarket support. A number of basic bolt on mods like an intake, exhaust, tuner, and intercooler should be able to take the 3.0L V6 from 349hp to 420-430hp pretty easily. These performance parts can be bought for just a few thousand dollars which makes it pretty affordable to push this engine closer to the power levels of the C43.
The stock turbo can handle about 500hp and 575lb-ft. of torque when pushed to the limit. You can achieve these power levels with the above mentioned mods plus some turbo inlets and outlets. However, the stock turbo will lose a lot of reliability at these levels. Turbo upgrades are pretty easy on the B9 platform and can actually get the S4 down into the high-9’s in the quarter mile, as seen recently by Integrated Engineering’s S4.
C43 AMG Power Potential
With higher factory output than the S4 the C43 has the advantage. However, the M139 engine is newer and therefore a bit more limited in terms of aftermarket support. One good sign for the C43 is that the C63 AMG actually uses the same engine and produces 469hp and 402lb-ft. of torque. Considering this is the same exact engine, the M139 is the C43 is likely just tuned down a little bit which means that some simple tuning can probably push it to the same power levels as the C63. This makes the C43 vs C63 and interesting debate as you can purchase a C43 for about $20k less and spend a couple thousand on performance parts to get it to the same power levels as the C63.
Weistec already has a tuner on the market that advertisers power levels up t 510hp and 490lb-ft. of torque. With the addition of a few more performance mods, the C43 AMG should easily be able to handle over 500hp without losing much reliability.
Winner: Mercedes C43 AMG
While the Audi is slightly faster from a dig, the C43 produces a lot more power from the factory and has more aftermarket potential. While the S4 can get around 500hp with some bolt-on mods pushing past that level will require some additional investment in an upgraded turbo. The C43 on the other hand can get to these power levels with just a tune. I suspect an upgraded turbo on the new M139 might be more challenging given the electric configuration, but is likely capable of providing better power gains compared to the S4.
C43 vs S4 Reliability
The B9 S4 has been around for a number of years so we have a pretty good idea of its reliability. With the C43, this is the first year of a new engine for this car. While the M139 has been used in a few other vehicles since 2019 it is new to the C-series and first year models tend to always have the greatest number of problems. However, we can gather a decent idea of reliability based on the other vehicles that use the M139.
C43 M139 Reliability
Mercedes claims that the M139 should be able to last 155,000 miles, or 250k kilometers, without needing an engine rebuild. While this doesn’t sound terrible in a brand new vehicle, it will have a significant impact on reliability in later years which will also impact resale value and maintenance costs. There are numerous performance engines on the market that can surpass this mileage without the need for a rebuild. One additional caveat is that this is for a stock engine. Reliability and engine life will decrease once you tune and modify it which gives us concerns over engine longevity on modified C43’s.
So far the M139 has proven to be quite reliable – however, all of these vehicles are still under warranty for the most part which makes it a bit more challenging to discover common problems. But with that being said, we don’t have any reliability concerns with the M139 at low miles. However, the rebuild lifespan gives us concern over higher mileage and modified M139’s.
S4 3.0L V6 Reliability
Part of the issue with the M139 is it produces 201hp per liter, which is pretty impressive. At 3.0L and only 349hp the S4 only produces about 150hp per liter which ultimately means there is less stress being placed on the engine. Problems with the B9 S4 so far seem pretty minimal with typical issues like injectors and ignition coils. Additionally, the water pump and PCV valve are known to fail. Ultimately, these are all relatively minor problems and more so general maintenance items.
We haven’t seen any material or catastrophic issues with these engines and there are plenty of examples of them surpassing 150,000 miles. Ultimately, the S4 has a leg up on the C43 in terms of reliability as its engine has been in use for 5+ years now and has proved reliable.
The S4 has a lower starting MSRP, around $52k. However, to get the S sport package with the upgraded rear diff, you have to choose at least the Premium Plus package and opt for the $2,500 S sport pack which brings the starting price to right around $60k. The C43 AMG starts right around $61k but doesn’t have any must-have performance packages, unless you want to upgrade the looks with the $3,700 performance studio package.
So, the starting price for both of the cars is virtually the same. The one caveat is that for the S4 you aren’t just getting the base model at $60k. You are getting the Premium Plus package which has a number of upgrades over the base model. With the C43 you are getting the base package and will need to add some additional packages to get the fancier navigation displays and all of that good stuff that comes with the Premium Plus S4.
Mercedes, in our opinion, is a bit more premium of a brand than Audi and so it’s understandable that building a comparatively packaged C43 is going to land you a bit above the S4 in terms of price.
C43 vs S4 Summary
The C43 AMG and Audi S4 are two cars that compete head to head when it comes to performance, luxury, and price. The S4 is a bit underpowered compared to the C43, with only 349hp compared to 402hp, but it is a smaller and lighter chassis which gives it a quicker 0-60mph time. However, the M139 engine in the C43 leaves a lot of potential open for increased power and performance with modifications. While the S4 also has good performance potential, it is a bit more restricted than the C43 unless you are planning on upgrading turbos.
The S4 is going to get a better reliability rating from us since the engine has been around for a number of years and has so far proved quite reliable. The M139 engine itself is pretty new, having been launched in 2019, and 2023 will be its first year in the C43 AMG which gives us concerns that there might be some first-year problems associated with it. Additionally, the 155,000 mile rebuild service on the M139 gives concern that higher mileage engines will prove to be expensive to maintain.
Overall, these are two great luxury performance features. Which one is better really depends on your preference for brand and desire for performance.