Should you buy or avoid a turbocharged car?
With tighter fuel economy regulations, more and more car manufacturers rely on turbocharged engines. With a turbocharger, the vehicle can have a smaller engine and use less gas when coasting, idling or in stop and go traffic. When needed, a turbocharger kicks in and provides extra power.
Are turbocharged engines reliable? Do they require more maintenance? How long can a turbocharged engine last? What should you watch out for when buying a used car with a turbo engine? Before answering these questions, let's start with the basics:
What does a turbocharger do in a car?
Volkswagen turbocharger. See larger photo
A turbocharger is a power-boosting device attached to the vehicle exhaust manifold. A turbocharger has two separate ports, exhaust and intake. A spinning shaft built into the turbocharger has small turbines installed on both ends.
One turbine is in the exhaust port (pink in the photo), another is in the intake port (blue in the photo). Hot exhaust gases rapidly exiting the engine spin the turbine inside the exhaust port. The shaft transfers the rotation to the intake turbine. The intake turbine pushes more air into the engine (boost). As more air enters the engine the engine computer also adds more fuel to add power.
Does a turbocharged engine require more maintenance?
The short answer is yes. The first reason is obvious: adding a turbocharger to a smaller engine makes it work harder. A turbocharged engine has a higher compression ratio, which adds more strain on all internal components including pistons, valves, and the head gasket. The harder the engine works, the faster it wears out.
The second reason is inherent in the design of a turbocharger: it has to work at extreme temperatures of hot exhaust gases, while the turbocharger shaft is lubricated by engine oil. This means there is more demand to the oil quality. Engine oil deteriorates faster under extreme heat. A turbocharged engine will not forgive low oil quality or extended intervals between oil changes. Most turbocharged cars need high-quality synthetic oil and have shorter maintenance intervals. Some also require premium gasoline.
Are turbocharged engines reliable?
There are turbocharged engines that are reliable, however in many cars, turbo engines tend to have more problems. A turbocharged engine has more components than a naturally-aspirated (non-turbo) motor. These include cumbersome exhaust components with the wastegate, intercooler, boost control system, vacuum pump and more complicated crankcase ventilation (PCV) setup. The more parts, the more can go wrong.
At higher mileage, as the cylinder walls and pistons rings wear out, higher compression causes increased pressure inside the engine crankcase. This can result in oil leaks that pop up from many places and often are difficult to fix.
That said, there are turbo engines that can last very long. Take, for example the turbodiesel in the Mark IV Volkswagen Golf / Jetta (from early 2000's). Many of them are going well past the 200K miles mark.
Are turbo engines good for towing?
If you plan to use your vehicle for heavy-duty towing, it's best to choose the vehicle with a larger V6 or V8 engine. A turbocharged engine is more suitable for quick bursts of power when passing or accelerating. Towing a heavy trailer, especially when driving on a long uphill road puts a lot of strain on a smaller turbo engine.
What to look for when buying a used car with a turbo engine?
White smoke from exhaust
Turbocharged engines tend to have specific problems. When test-driving a used car with a turbo engine, watch out for a white smoke from the exhaust (see photo). It could be just a small puff when the engine is started, but it means expect expensive repairs. Some turbocharged engines are known to consume oil. Watch out for low oil level which might indicate higher oil consumption. A failing turbocharger might produce a screeching or whining noise at certain boost stages. Another symptom of a turbo going bad is lack of power (boost) on acceleration. Read more: How to inspect a used car.
Watch out for oil leaks. The first symptom of oil leaks is a smell of a burnt oil coming from under the hood. It's a good idea to have the second-hand vehicle inspected by your mechanic. He (she) can lift the vehicle and check for oil leaks underneath, as well as inspect many other components. Ask your mechanic to visually check the condition of inside engine components if possible. Black deposits covering the oil dipstick or lodged under the oil filler cup inside the engine indicate poor maintenance. It's best to avoid a vehicle with a turbo engine that shows any signs of lack of maintenance. Read more: how to check the engine in a used car.