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you & your car

2013 Subaru WRX STI has a 2.5-litre engine with a turbocharger.

Nowadays car manufacturers are going for smaller engines boosted by turbos. When this trend started, the reliability of turbos was not good and repair costs were high. I think it was because they revolved at high speeds. What is the present situation regarding turbo maintenance? – Declan

We've come a long way since those early turbos and, like everything else, reliability has improved and costs have fallen as they came into more widespread use.

The principal issue was not so much the rotational speed involved, but rather the heat generated and the effect it had on lubricants.

Turbochargers, or turbos as they are commonly called, are located within the exhaust system and depend on exhaust gasses forced out of the engine to spin a turbine that is directly connected to a compressor, which forces more air into the engine. That in turn allows more fuel to be mixed in, resulting in more power without having to revert to a larger engine. In simple terms, a turbine on one end of a shaft is in the exhaust stream while a compressor on the other end of the same shaft is in the intake stream.

The turbine is in direct contact with exhaust gasses that can be as hot as 1,200 F or 650 C. Early turbocharged cars suffered from problems caused by that heat when it literally baked the oil used to lubricate the bearings if the engine was shut off with the turbo still hot. Because the oil was no longer circulating, that part of it still in direct contact with the turbo became overheated. This led to the instructions to let the engine idle for a moment or two before shutting it off, allowing the oil to circulate and cool things down. Subsequently systems were developed to ensure the oil circulated for a period of time even if the engine was shut down.

A number of advances have taken place in the intervening years that have all but eliminated this issue. Most of them are related to improved cooling methods, but advances in lubricants recommended for turbocharged engines and the physical makeup of the turbos themselves have also helped.

A current turbocharged engine requires little more maintenance than other engines. As is always the case, oil changes play a key role and, in a related matter, so does reading the owner's manual to determine whether your driving habits place you in the normal or "extreme" or similar category. That does not mean racing, it means everything from infrequent use and short driving cycles to towing or carrying heavy loads, all of which place an added load on engine oil.

Servicing hybrids

We're looking to buy a used 2010 hybrid Lexus RX 450 and wondered about its performance over the last two years? Are regular service stations able to service them? – Sandi

The Camry-based RX has been a model of reliability since it was introduced in 2006. The hybrid version uses components proven in other Toyota/Lexus models and I am not aware of any problems particular to that specific drivetrain.

As for service, the engine, brakes, exhaust system, interior parts and pieces, suspension, etc., are common with a number of Toyota/Lexus vehicles, so parts and service should be readily available. The electric motor, CVT and associated components, however, should be left to a qualified Toyota/Lexus technician, not only because of their complexity but also the extremely high voltage and attendant safety factors. The good news is that there is little, if any, service required for these systems.

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