BMW B48 vs B58

To some extent, it may seem foolish to compare the BMW B48 vs B58 engines. After all, the B58 is a 3.0L inline-6 that delivers up to 382 horsepower. The B48 is a much smaller 2.0L inline-4 that offers up to 255 horsepower. In that sense, these engines are targeting two different markets. However, is it really worth upgrading to the B58 40i models or does the B48 offer enough? In this guide, I compare B48 vs B58 specs, performance, reliability, and cost.

Engine Specs Comparison

*There is a more powerful variant of the B48 with significant changes including a lower 8.9:1 compression ratio. The B58B30O1 uses a 10.2:1 compression ratio.

Looking over the specs, you may believe the B58 is nothing more than a B48 with two extra cylinders. That’s not far from the truth. In fact, that’s largely the purpose of BMW’s B-series engine family. It’s a modular engine family which means much of the design is shared in common and many components are interchangeable between the B48 and B58.

As such, outside of displacement and cylinder count, the two engines are very similar. The B58 does have a number of different components to support the larger displacement and power potential. For example, it uses a bigger turbocharger. However, many of these small changes aren’t worth diving into specifically.

BMW B48 vs B58 Performance

Looking at factory performance, I won’t dive too deep into specifics about 0-60, 1/4 mile, etc. The B48 & B58 are in dozens of different models and performance varies by each. That’s especially true considering the engines also have varying power output. However, there are some general concepts that apply to the B48 vs B58 comparison.

The B58 has the cylinder and displacement advantage. It delivers roughly 100-125 horsepower more than the smaller 2.0L inline-4. It’s simply the better performance engine. That’s true in both stock form as well as with aftermarket upgrades, which I discuss in a moment.

Most B58 models will reach 0-60 about 1 to 1.5 seconds quicker than the B48. As one specific example, the 2023 M340i xDrive achieves 0-60 in 3.7 seconds. The 330i xDrive is 1.5 seconds behind, requiring 5.2 seconds to reach 60mph. The gap grows in the 1/4 mile where the M340i runs it in 12.2 seconds @ 112mph compared to 13.9 seconds @ 100mph.

Now, that leads me to the final point before moving onto aftermarket performance. This is an engine comparison and not necessarily a model comparison. However, the B58 is in higher-trim BMW’s. Using the same M340i vs 330i example, the M340i is more than just an engine upgrade. It also features better tires, better brakes, etc. from the factory.

Aftermarket Upgrades

This is the part where it’s easier to isolate the vehicles and focus strictly on the engines. Both the B48 and B58 are incredibly strong and capable engines. Tuning and basic bolt-on mods are generally safe and do not put the engine at greater risk of failure or serious problems. Ultimately, the engines are much stronger than what they’re tuned to from the factory.

The B48 can achieve 275-300whp and 290-320wtq relatively easily with a tune, intake, downpipe, and small E85 blend. That’s a considerable amount of power for a fun, sporty daily driver. The engine can handle 375-425whp relatively safely with an upgraded turbo and fueling mods.

On the other hand, the larger BMW B58 can make an impressive 450-500+whp with the same tuning and basic bolt-ons. For some, that’s already pushing into the realm of too much power for a daily driver or street car. Those wanting more will find no shortage of options. The B58 can safely handle 600-700+whp with turbo and fueling upgrades. 1,000+whp is even possible with a built motor.

B48 vs B58 Reliability

Reliability is a pretty quick topic for the B48 vs B58. Both engines are very reliable and big improvements from many BMW engines around the 2000-2015 era. Neither engine is perfect, but they’re darn good. If you’re interested in learning more about reliability check out our B48 common problems and B58 common problems guides.

As for the B48 vs B58 comparison, there isn’t a clear winner for reliability. A lot of it simply comes down to maintenance, repairs, and some luck of the draw. However, there are a couple other related topics to discuss.

The B48 is the smaller 2.0L inline-4 engine. Two fewer cylinders and a smaller displacement will naturally lower standard maintenance costs. 4 spark plugs and ignition coils versus 6, smaller oil and coolant capacity, etc. That’s not going to make a huge difference at each service interval. It does, however, add up over the lifetime of the engines.

Where the B58 potentially holds a longevity advantage is when talking about aftermarket upgrades. The larger displacement is better able to manage heat and stress. An inline-6 is also a superior engine design in that it’s perfectly harmonically balanced.

It all comes back to neither engine having a significant reliability or longevity advantage over the other. Some B48’s will outlive some B58’s and vice versa and a lot of that will boil down to luck of the draw and maintenance.

Price Comparison

Thus far, we’ve discussed that the B58 has the performance advantage and reliability is a wash between the two engines. Price is where things take a turn in favor of the B48. Circling back to the performance topic and using the same example let’s look at some pricing:

• 2025 330i xDrive: $47,500 MSRP
• 2025 M340i xDrive: $61,600 MSRP

Again, the difference in vehicles is more than simply the B48 vs B58. The B58 is only available in the “M-Lite” trim, which means it has some extra performance parts and goodies. Still, that $14,100 difference in MSRP is big.

The exact difference in price varies dependent upon which model(s) you’re comparing. However, when comparing similar models the price difference is generally about $10,000-15,000 to upgrade to a B58 powered model. Differences in prices start shrinking a little when looking at used models. Still, expect the B58 to be at least $7,000-12,000 more expensive for a similar model and condition.

Is the B58 Worth the Extra Cost?

This is a subjective question, so there isn’t any one answer that fits all. If you have the means to afford it comfortably and value performance over all else then the B58 is likely worth the upgrade. If you’re worried about costs but still value performance over all then maybe consider a B58 that’s a couple years older. Or save up for another year or two.

In essence, if you’re looking for maximum performance then you may end up regretting the purchase of a B48. It’s a great engine and 275-300whp with basic bolt-ons is still good performance. However, once you’re hit with the power-bug it’s tough to stop there.

On the other hand, those who don’t put a high value on maximum performance will likely find the B48 as the more suitable engine. It’s fun, sporty, and delivers plenty of performance for an A to B daily driver. It also does so with lower maintenance costs and better fuel economy.