2018-2024 BMW 3-Series M340i 3.0L Turbo Engine (B58): Problems, Longevity, and Specs

The 3-Series model is one of the not-so-many-left compact sedan cars on the market. And it still sells like crazy if you compare those sales figures with other vehicles of the class. On average now, about 200 people a day in America get their new 3-Series sedan cars from BMW showrooms and this is huge.

I've already told you about base trim levels engines used in this model and today, I want to show you the most powerful version. In this article, I will tell you about the M340i engine in the BMW 3-Series which is the 3.0L Turbo unit - a really sporty BMW machine that obviously deserves your attention.

Key facts and my opinion about the engine

• Production years: 2015-now
• Average lifespan of B58: 180,000-200,000 miles
• Fuel supply type: direct injection
• Power range: 326-388 hp
• Fuel efficiency: average
• Engine block material: aluminum
• Engine reliability score: medium
• The most common problems: coolant level mysteries, head gasket failure, carbon buildup on intake valves, VANOS issues.

What should you know about the 3-Series M340i engine?

This is the most powerful engine that you can get in the modern 3-Series. Well, when you see the letter "M" in the name of the trim in a BMW car, you may be sure you will love it. Unfortunately, all "M" engines are made with the priority of power but not longevity, but this is a hard topic that may cause a lot of arguments, so let's approach it step by step.

So, the M340i engine will most likely take your breath away when you start driving this car and it's really hard to get used to this feeling. It will go 0 to 60 MPH in reportedly 4.1 seconds. This is good even for a sport-oriented car. It's hard to translate into words what you will fill when you first time drive this beast.

Here are some of the key features of the engine:

• this is the 3.0L gasoline turbocharged 6-cylinder inline engine that is codenamed B58;
• the engine offers 382 horsepower and 368 lb-ft of torque, the torque is available very early (at low RPM) and this feels just wonderful;
• the engine is available in two versions - the rear-wheel drive and also the xDrive;
• the engine is equipped with the 8-speed ZF automatic transmission - quite a good transmission for this kind of car;
• both camshafts have VANOS phasers and also the engine is equipped with Valvetronic;
• the timing system is driven by chain but it's not going to live forever, so no good news here;
• the turbocharger is the twin-scroll unit that is the main hero in this powerplant (Bosch or Mahle units are used);
• you can get about 23 MPG in the city and 31 MPG on highways, but don't rely on those estimated figures.

The fuel economy looks great on paper. But of course, it won't be that great in real life. You will probably get about 18 MPG in the city traffic because your right foot will be itchy to press that wonderful gas pedal and get that unbelievable feeling of crazy acceleration. So, gas mileage is obviously not the feature you will be taking into account when buying this car.

The engine looks pretty good. BMW even made special iron coating in the cylinders to protect them from overheating when the engine is revving up like crazy. The engine has been manufactured since 2015 and so we know all the bad sides of it now. And I can say it's a really good and decent engine with no critical issues at low mileage.

How many miles will the B58 engine last in your 3-Series?

Your BMW engine is going to last quite long if you maintain it properly. The M340i engine has quite a decent displacement and isn't over-boosted, it was updated in 2018 to solve the problem of the complicated timing system with two chains. Now it has one chain and the system is easier to repair and maintain.

I believe you can easily take your BMW 3-Series M340i engine to 200,000 miles if you don't use it for racing. If it constantly works at extremely high RPM, the engine will not survive that long. So, very aggressive driving that turns out to be your normal driving style will obviously kill it much earlier than 200K miles.

The 8-speed automatic transmission engineered by ZF doesn't seem to be bad at all. I don't think it will survive as long as the engine, but you won't repair it lots of times. I believe, one minor repair will be needed at about 120,000 miles and the transmission is good to go for 200K miles or even more.

Overall, this seems to be one of the best high-performance engines on the market in terms of durability.

What are the common problems with this engine?

Well, I perfectly know that there are no perfect mechanisms and the BMW 3-Series M340i engine is not an exception. Though I don't want you to think that I'm searching for some bad sides to discourage you from buying this car. I want to underline here that I absolutely love this engine and think that it's worth every dollar you pay for it. This is uncommon for me because I love criticizing modern technologies in cars.

But still, it's fair that you know the possible problems you can have with this expensive powerplant. And here they are:

1. Magic antifreeze issues

For several weeks you may control the antifreeze level every day and it will be OK. But one day you open the hood of your new BMW and see that the coolant is lower than the MIN mark. So, this is one of the mysterious problems that no one knows the reason for. The coolant just evaporates and mechanics can't tell you where exactly it goes.

I've heard that owners replace the coolant reservoir cap and it helps for some time. But I couldn't find a single idea of where the coolant leaks in these engines that you can trust, so just keep an eye on the coolant level.

2. Weak head gasket

The engine is really hot when it works at high RPM (pretty much always) and this causes premature death of the head gasket. Of course, this is an expensive problem but it doesn't mean that the engine will immediately die. You just shouldn't ignore the issue.

In most cases, when the head gasket is broken in the B58 engine, it means that you will see quite a lot of smoke from the tailpipe and will even smell the burning oil in your car and around it. Overlooking these symptoms is almost impossible. You should stop the engine immediately and find a tow truck that will deliver the car to the dealership or to the repair shop.

3. Bad idling due to carbon buildup

This engine is equipped with a direct injection system and it can lead to carbon buildup on the intake valves. So, after 30-40 thousand miles, the buildup will not allow the valves to close completely and this will obviously lead to issues like poor idling RPM, problems with acceleration, bad gas mileage, etc.

You should have the valves cleaned at least every 50,000 miles. But if you notice the problems earlier than that, you should go to the dealership or to a trusted shop and have them cleaned or at least checked.

4. Vanos and Valvetronic problems

Unfortunately, at 100,000 miles and more, you will have to deal with some problems with VANOS solenoids and the Valvetronic system. The variable valve timing will need cleaning, replacement of solenoids, adjustment, etc. quite regularly. Unfortunately, this is common for all engines equipped with these systems. They make the engine fuel-efficient and powerful but at high mileage, these technologies need a lot of investment.

5. Other minor issues

As with any high-performance engine, you will take your M340i to the shop or to the dealership quite often. Problems like overheating, failing engine sensors, bad idling, poor acceleration, bad start, and so on will obviously be chasing you all the time. Of course, the higher the mileage, the more problems you will get.

Can you prolong the life of this engine?

The M340i engine in the 3-Series is quite good and all you need to do to prolong its life is not to kill him with your driving style. Also, remember that BMW has a wonderful maintenance plan and if you just follow this plan, you will be able to reduce the number of problems.

In terms of driving style, I don't encourage you to drive your BMW 3-Series M340i slowly. This car is made for fast acceleration and aggressive driving and the engine will be OK if you do so. But there is a border between aggressive driving and abuse. Don't abuse your 3-Series because this is not the car for sports.

If you just follow these simple tips, you will be able to drive your BMW 3-Series for quite a long time and without many problems. But put up with the idea that sometimes, you will still need to go to the dealership and pay some money to get your small beast back on the road.