That was the question I received via email this week. Our reader was having doubts whether to invest in a Renault Clio 1.2. Not the Renault part, he was quite happy to buy the French marque. It was the fact that the engine is turbocharged, and judging by the question, he believed that turbocharged vehicles are less reliable.

The Stigma of turbocharged cars

I am not quite sure at which point turbos got the stigma of being unreliable. The first turbocharger was invented by Swiss engineer Alfred Büchi at the turn of the last century. He received a patent for this ground-breaking technology in 1905, and he saw the first real life application of his invention, believe it or not, on large marine engines during World War I.

A hundred years on, you would be hard pressed to find a European manufactured vehicle range which does not feature turbocharged engines. Approximately 70% of all vehicles sold in Europe today, whether petrol or diesel, are turbocharged. Due to Euro emissions legislation, the big capacity engines of yesteryear have made way for small-capacity turbos.

Turbocharging has proven to help smaller engines deliver the performance of larger ones - but with the added advantage of improvements in fuel consumption of up to 40% in diesel engines and up to 20% in petrol engines. As a result, turbodiesel passenger vehicles are becoming more commonplace around the world, and the availability of latest generation fuel turbo systems, matched to direct injection technology, is creating the ideal conditions for an engine downsizing strategy without having to sacrifice performance.

Turbo’s today are better than the turbo’s of yesteryear

Of course, in the same way as engines have become more powerful, more reliable and more technologically advanced over the last 100 years, so too have turbos. The 1920 Ford Model T had a 2.9-litre motor which produced 14.9 KW. An average 2.9 litre motor today produces in the region of 160 KW.

There is no negating the fact that early turbos had their issues. Turbo’s would quite literally blow up, bearings were prone to failure, and oil consumption was known to be excessive. However, turbo technology has a long way since then, and the modern-day turbo is far more reliable than those of the 80’s and 90’s.

Modern turbocharged engines have been designed from the ground up to be used with a turbocharger, and complete hundreds of thousands of kilometers of simulated testing before making it into production. Engine parts that are subjected to the increased stress of turbocharger operation are beefed up to deal with the additional stresses, and are typically trouble-free. The modern turbocharger has evolved with better bearings, better cooling, and better lubrication in addition to improved metallurgy.

The way that a turbocharger is controlled has also improved dramatically. In place of primitive mechanical waste-gate controls, there are now a bevy of sensors reporting engine and environmental conditions to the powertrain control module, or PCM, so at all times, turbocharger operation is carefully managed. If conditions such as hot and dry air, a lean air-fuel ratio or engine ping are encountered, turbo boost is reduced, along with other possible protective actions.

Turbocharger surge, a condition that can occur during sudden throttle closure, can whipsaw intake pressure enough to damage the turbo. This used to be a real problem back in the day. Nowadays, it is largely mitigated with additional controls. Variable-rate turbochargers are also popular, allowing a larger turbocharger to act like a smaller one at lower speeds and spool up more quickly. This improves torque across a wider rpm range, which really enhances drivability.

So, while turbochargers have vastly improved over the past few decades, would a turbocharged engine ever be as reliable as a normally aspirated one?

But are they as good as a normally aspirated engine?

While there may still be lingering negative sentiment towards turbochargers, the fact remains that turbocharging is becoming increasingly popular. Whether we like it or not, downsized, force-fed engines are being increasingly used to replace larger naturally aspirated units. Oftentimes, these powerplants are more complicated than the ones they’re substituting, with intercoolers, extra oil lines, convoluted plumbing and more potential headaches down the road.

In other words, turbocharged engines are more complex. And whenever you add complexity, you add potential areas of failure.

Additionally, a turbocharged engine is more “stressed” than a free breathing naturally aspirated engine. This means that the engine has to work harder, at higher temperatures and at higher pressures. So, in theory, you would expect it to wear out quicker?

Yes and No

The answer is not necessarily. A 2018 study entitled “Troubles With Turbo Engine Reliability” by Consumer Reports (CR) looked at which brands have turbocharged engines with reliability better than the average reliable of non-turbo engines. And which have worse reliability.

The study found that six brands which have turbocharged engines with better reliability than the average non-turbo engine. These brands were Honda, Lexus, BMW, Porsche, Audi, and Subaru.

A longer list of brands offers turbocharged engines that fall on both sides of the average for reliability when compared to non-turbo engines. Ford and VW have multiple different turbo engines that are both better than and worse than non-turbo engines in terms of reliability, depending on the exact engine.

And then were the brands whose turbo engines were less reliable than the equivalent non-turbo engines. These were Mini, Hyundai and Chevrolet.

One may argue that these results were based a small sample size and that reported problems were not necessarily weighted in terms of severity. I mention it not to promote one brand or disparage another, but rather to underscore is that not all turbo engines are the same. And when questioning whether turbocharged engines are reliable, we should talk about individual engines and not necessarily bundle them all into one generalized group.

If you are looking at buying a particular car, I suggest researching that car and that engine in particular. Read consumer reviews, road tests and user forums. Try asking your mechanic what he thinks of the particular vehicle you are considering, and if possible, speak to other owners of the same vehicle about their experiences. You will quickly be able to ascertain how reliable the vehicle is, and what the expected lifespan is.

There is a wealth of information on the internet. However, a point I often remind people of is that, in some instances,  reported issues often appear to be a lot worse than they might be in reality.

Problems can seem much more common on an active internet forum than they actually are. For example, if there are a few thousand members on a car forum and even just a small percentage have a problem, it can seem like everyone’s having the problem because you see the same thing reported 20 or 30 times.

The question of cost

The fact that a vehicle is not reliable, or not as reliable as it’s peers, does not necessarily mean do not buy it. It comes down to cost and value. I suppose the same goes for buying a turbocharged car as opposed to a naturally aspirated-one.

Consider the following hypothetical scenario. For your given amount of cash, you can purchase a 1.6 liter normally-aspirated car, which uses 8l/100km. Or you can purchase a 1.0 turbo, (which makes the same power), but uses 5l/100km. Now the lifespan of the turbo is, let’s say, 150 000km and the 1.6 lasts, well… forever.

By the time you reach 150 000km, you’ve used 7 500 litres in the 1.0, or 12 000 litres in the 1.6. At R15/litre, that’s R112 500 or R180 000, respectivley, which means that you have saved R67 500 in fuel alone. Now, what does it cost to replace the turbo?  Maybe R15 000 on average? So yes, I definitely see the logic in buying the turbo.

You could follow similar logic when considering two turbo vehicles. If car A’s turbo lasts 200 000kms and car B’s lasts 100 000kms, but the purchase price of B is, let’s say, R30 000 cheaper. A quick look on the Start My Car website shows that a replacement turbo for car B costs R7500. Let’s even make that R10 000 with labour. It still makes good financial sense, to buy Car B. You are saving R30 000 now, and possibly have to fork out R10 000 in a few years time.

So, when considering buying a new vehicle, spare a thought if it was worth paying more now for ‘supposed’ reliability, or whether it is cheaper to deal with ‘expected’ problems when they arise.

In Summary

I’ve  have read perhaps a dozen quotes by car company powertrain engineers claiming modern turbocharged engines are just as reliable as naturally aspirated ones, and speaking with mechanics who actually fix them seems to largely confirm this. Yes, some turbo’s are better than others. But the same goes for normally aspirate engine’s too. Not every 3.0 V6 out there is equally reliable.

However,  this isn’t to say one can neglect maintenance. Turbocharged engines are more demanding on engine oil and work harder than a larger, naturally aspirated engine making similar power. I’d have no problem owning one and giving it the maintenance respect it deserves.

Lastly, in addition to the regular maintenance, there are a few driving style changes you may need to learn to get the most from your turbo engine, and to avoid nasty repair bills. We will discuss these in next week’s article.

So long. Keep safe