Back when cars were cars rather than smartphone on wheels, the world was quite simple. You either used Netscape Navigator or Internet Explorer, liked either Honda or Toyota, before graduating to either the BMW or Mercedes-Benz camp.

If driving performance is what you seek, a BMW is the one to buy. No one disputed its Ultimate Driving Machine tagline. The BMW 3 Series conquered touring car races across Europe, and was the default choice for young stock brokers in London’s financial centre in the roaring ‘80s.

Meanwhile, BMW’s chief rival Mercedes-Benz took great pride in building cars that lasts, and they have a longer heritage to back up their claims.

‘Engineered like no other car in the world’ was the promise of cars bearing the three-pointed star. It’s a promise that taxi drivers all over the world, from Africa to Germany, as well as Ipoh’s tin mining tycoons and Russian oligarchs bought and believed in.

Also read: Steeped in heritage, Mercedes-Benz Malaysia’s most important Ipoh outlet gets an upgrade

“BMWs are fast, but Mercedes-Benzes are more reliable” is something that many still believe until today, even though cars made by both brands are now conceptually identical, all powered (mostly) by turbocharged 2.0-litre 4-cylinder engines.

We’ve done quite a number of used car buying guides for many popular BMW and Mercedes-Benz models, covering the F20 1 Series, F30 3 Series, F10 5 Series, W176 A-Class, C117 CLA, W205 C-Class and W212 E-Class. We've even covered the very popular 330e. If there is one common theme, it is that there is no such thing as a problem-free BMW or Mercedes-Benz.

These cars are quite complex and keeping them on the road is going to cost you a bit more money than say, a Toyota Camry.

BMWs are less reliable than Mercedes-Benzes? No longer true in 2022

Back in the ‘80s and ‘90s, it is true that BMWs are quite rubbish when it came to reliability. A W124 or W201 is more reliable than a contemporary E34 / E39 BMW 5 Series or E30 / E36 3 Series. It’s not just mechanical issues, but also body construction as early BMWs rust a lot faster than thicker steel-gauge bodied Mercedes-Benzes.

But today’s BMW is not the same BMW that made those sleek shark-nose beautiful cars everyone who grew up in the ‘80s and ‘90s lusted after, for better and for worse.

Today’s BMWs are ugly, what was called the signature kidney grille is now the signature swine nostrils, but today’s BMWs are also so much better built.

The previous F30 generation BMW 3 Series, especially the newer B48 engine-powered LCI facelift model, is one of the most reliable German cars ever made, never mind a BMW.

Even on the supposedly more problematic pre-facelift N20-powered models, problems with oil leaks and water pump failures are exaggerated. Fixing these are a relatively simple, one-time job costing only several thousand Ringgit (fair for its age), usually required only at mileage way past 100,000 km.

Also read: F30 BMW 3 Series: Still the best 3, tips to buy good used ones for RM 100k

Also, just as today’s BMW is no longer the same BMW from the Ultimate Driving Machine days, today’s Mercedes-Benz is also not the same Mercedes-Benz that made cars your father or grandfather drove.

If Mercedes-Benz had continued taking 8 years (the time taken for the ‘70s era W123 E-Class) to develop a model, spending more time and money in unnecessary over-engineering, the company would no longer be in business today.

Today’s Mercedes-Benz, like any BMW, has many more parts that are not developed by Mercedes-Benz, more than ever before. This is because it’s cheaper and faster to buy off-the-shelf parts developed by the likes of Bosch and Continental, than to do it in-house.

Today’s customers want the latest in technology, just like their smartphones, and it’s not possible to keep up with the pace of product development if the company is to insist on doing so many things in-house, in the same way as before.

Starting with the E39 5 Series in the mid '90s, BMW made great strides in quality. Dashboards no longer crack, galvanized steel bodies resisted rust better (earlier galvanized bodies were laughable), engines were less finicky. 

Compared to the W210 E-Class, which was a low point for Mercedes-Benz quality, the gap between BMW and Mercedes-Benz were negligible, and both improved further from that point onwards. 

So has Mercedes-Benz become less reliable then? Not true. Far from it. Like many modern cars, they are more reliable than ever before, but only up to a certain point.

Today’s cars are far more complex, far safer, have a much longer 15,000 km/1-year service interval. So long as you don't try to save money on preventive maintenance, they work flawlessly, until you've passed the 15-year / 250,000 km mark (disagree? Hold on, we will come back to this later). The way the manufacturer sees it, you should've changed your car by then.

Making the car last any longer is also not in the interest of the customer, because that would mean either higher prices or lesser features. Customers say they want a long-lasting product, but few are willing to pay for it, so they are not going to get it.

Between bigger touch screens, fancy tech, and sexier alloy wheels at lower prices versus Toyota-style tried-and-trusted basic tech-only but longer service life, the former always wins, always. Just look at Uniqlo's and H&M's fast fashion and the lifespan of smartphones.

Today's consumer products don't need to last decades, they only need to last long enough until something fancier gets their attention and it's time to change.

BMWs and Mercedes-Benzes are very reliable, just not the ones us Malaysians normally buy

If you want to experience a BMW or a Mercedes-Benz the way its manufacturer idealised, you will have to buy models with diesel engines.

Before Dieselgate and when investments into combustion engines were at their peak, the best engines BMW and Mercedes-Benz had to offer were diesel ones. This is because more than half of all passenger cars sold in Europe were diesels (petrol and petrol-electric hybrids now dominate). Diesel engines were their bread and butter and they cannot disappoint their fellow countrymen, especially Germany’s notoriously fussy taxi drivers.

A diesel-powered BMW or Mercedes-Benz has the reliability to match a Toyota, and there are plenty of E-Class taxis in Germany with half a million km on the odometer to back up that claim.

Unfortunately for us, these very durable diesel engines need low sulphur diesel fuel to run (and expensive AdBlue liquid for the exhaust).

Although Malaysia has since caught up with Euro 5 diesel, it’s too little too late as neither brand is interested in spending money to promote diesel engines, which are already nearing the end of their lifecycle in Europe. In the post Euro 6 emission standards era, there is not much future for diesels.

Both German brands are now in the midst of transitioning to electric vehicles. Diesel engines are not on their agenda.

Also, Malaysia’s palm oil-blended B10 biodiesel is not compatible with European diesel engines. Actually, no German car manufacturer has gone on record to say that warranty for cars running on anything higher than B7 biodiesel (the current standard for local Euro 5 diesel) will remain intact.

So should you only buy a used German diesel model and avoid petrol ones?

It would be unfair to say that German petrol engines are unreliable, because they do make very good petrol engines, especially higher capacity 6-cylinder ones.

Buyers need to understand that when they buy a used BMW or Mercedes-Benz with a 4-cylinder petrol engine, that this engine was never the top priority for the Germans.

The order of priority for German car companies are: First - economical and low running cost diesels for the masses, Second - high capacity performance-oriented petrols for keen drivers, Last - small 4-cylinder petrols for everyone else who can’t accept the first two options.

This explains why European drivers don’t understand us Asians when we say that European cars are less reliable than Japanese cars.

At least this was the order of priority until Dieselgate happened in the mid 2010s.

There's good news, diesel is out, latest petrol engines are very reliable

The good news is that the current generation of petrol engines by BMW and Mercedes-Benz are very reliable. BMW's B48 for example, is its most reliable ever. Likewise Mercedes-Benz's M254 mild-hybrid, which now uses an integrated starter motor (ISG) rather than the previous M264 engine's rather iffy belt-driven starter motor (RSG).

Post-Dieselgate, demand for diesel engines for passenger cars in Europe has collapsed, now standing at just under 20 percent. Petrol engines, including hybrids and plug-in hybrids, make up nearly 70 percent of new passenger cars sold in the old Continent.

This has prompted a shift in priority, which also explains why the current generation of 4-cylinder petrol engines from BMW and Mercedes-Benz are so good.

BMW or Mercedes-Benz, buy what you like but pay attention to maintenance

In conclusion, it is no longer true that a BMW is less reliable than a Mercedes-Benz. These days, there's not much separating the two.

However if you are buying a used BMW or Mercedes-Benz made before the 2010s and insists that they should be as problem-free as a Toyota, try looking for a 6-cylinder model, or a diesel-powered one like a 320d or a 520d or an X1 xDrive20d.

Having said that, diesels are not for everybody, even though they offer excellent mileage.

If you stay in a landed property, you may notice diesel soot or diesel exhaust smell entering your house every morning you start your car, even with closed doors or windows.

It is for this exact reason that diesel cars are sold in Europe with diesel particulate filter and AdBlue after-exhaust treatment – both removed on many European diesel cars sold here to make them compatible with our then-lower grade diesel.

What about petrol engines? Preventive maintenance is the key. These are not pump petrol-and-go cars so take some effort to understand the car. Not every maintenance job recommended by your mechanic is done so he can rip you off, so it is important to have the car’s maintenance done by a trusted workshop.

We personally recommend Munich Precision, but if you are looking for something cheaper, you may also try JW Performance – a small neighbourhood workshop that only has the capacity to take on regular customers, but the owner Jason is an honest, highly skilled mechanic.

Carsome has a wide range of quality used BMW 3 Series and Mercedes-Benz C-Class, backed by a 1-year powertrain warranty, and 5-day money-back guarantee.