How often should I service my vehicle?
To state the obvious, "follow the vehicle manufacturers guidelines", would be the easiest way to write and finish this article, however in my opinion, most vehicle manufacturers do not deliver enough information to the purchaser of a turbocharged vehicle...
Oils and Oil Filters:
At a minimum "follow the vehicle manufacturer's guidelines" although our normal policy is to change oil every 5,000 Km and oil with filter every 10,000 Km.
Why? The engine oil is not only the lubricant for your engine but it also lubricates your turbocharger but just as importantly, also acts as a coolant for the turbocharger; it removes the majority of heat from within the turbocharger which otherwise would cause components to expand, tolerances to change and turbocharger failure. Heat transfer via oil is also important on water-cooled turbochargers as well even though the temperatures within these turbocharger aren't quite as high.
Unlike a normally aspirated engine, oil in a turbocharged vehicles loses its viscosity a lot quicker due to the heat as mentioned above hence the oil requires changing more frequently. Low viscosity oil in a turbocharger can affect its cooling, lubrication, flow and pressure properties. You may "get away" with overdue oil changes on a normally aspirated engine but you will be repairing your turbocharger regularly if you attempt the same on a regular basis with a turbocharged vehicle.
The shortest period of time I can remember seeing a turbocharger fail due to total lack of maintenance and/or hot shut-downs on a new vehicle was on a 1990 Ford Capri 1.6 litre soft-top driven by a sales representative which only had 16,000 Km on the clock. The IHI turbocharger and attached piping were totally carbonised and oil couldn't flow through anything within a foot of the turbocharger, in addition the turbocharger wheels were locked solid "probably luckily" and hence his initial "lack of power" problem was solved. I remember him or rather his boss being very lucky as decarbonising the turbocharger and ancillary piping etc. and installing a service kit sorted out his turbo problem a lot cheaper than his company would have paid from a dealer whom would have fitted a new turbocharger and associated parts.
Conversely I have seen many a turbocharger on well maintained vehicles still in "as new" condition with well over 200,000 Km on the clock.
As far as the type of oil used varies considerably so again "follow the manufacturer's guidelines" although obviously its near impossible for a workshop to stock every brand and grade of oil.
There are a lot of good modern oils and I'm not promoting any particular brand however as a very general guide we would use a quality mineral based oil in older turbocharged vehicles, a semi-synthetic in newer vehicles and a full synthetic in late model vehicles. I do follow the grade of oil as recommended by the vehicle manufacturer on newer vehicles so the owner can maintain his warranty without any hassles but my main point which I keep harping about is the "frequency of oil changes using a good quality oil" rather than purchase the most expensive oil you can find nor the cheapest.
As a side note, synthetic oils also require changing just as frequently on a turbocharged vehicle as mineral based oils so don't fall for the "20,000 Km or more between oil changes" as per advertisements you may read or see on TV. This may be true for normally aspirated engines but not turbocharged engines.
One last tip on oils; when you pull up at a service-station and find you need to top up your oil, if you're using a synthetic oil make sure you top it up with a synthetic oil and not a mineral based oil and vice-versa, an oversight easily enough done. I've found the mixture of synthetic oil with mineral oil and heat over time is a great recipe for a blackish thick goo should you need to paint the back fence.
At a minimum, clean and/or change as per the "the vehicle manufacturer's guidelines" however I would firstly like to point out a couple of instances where air filters caused problems and I guess the point is don't take anything for granted, work in a clean environment and always re-check.
A few years back and I can't remember whether it was the Holden Rodeo or Jackeroo but we started to receive a flood of IHI turbochargers in for repair all with the same problem; the turbochargers were leaking oil both from the front and back piston ring seals which is normally associated with engine blow-by. The turbochargers were off relatively new vehicles most of which were serviced properly but they all had a common yet unusual additional fault, the edge of the compressor wheels were pitted as if mice had been nibbling at them which normally indicates dust contamination.
I enquired with the owners and/or mechanics as to whether the air filters had been changed and indeed they had been but we soon discovered a particular brand of cheap air filter was 5 millimetres shorter than the original even though it was listed for this particular vehicle and consequently didn't seal in the air filter canister properly leaving a gap for dust to enter the intake system.
Unfortunately for the owners of the vehicles the dust acting as an abrasive scored the bores of the cylinders allowing for engine blow-by to occur and as a consequence the turbochargers leaked oil. The engines required a rebuild and most of the turbochargers required a new compressor wheel and service kit.
Lesson learned; not only is it important to clean and change your air filter regularly but you should check it is sealed in the air cleaner assembly properly, nothing is accidently dropped into the air cleaner assembly whilst changing it and all the intake hoses and pipes are in good condition and clamps properly tightened.
A quick note on performance air filters; On a chasis dyno we tested some performance air cleaners from the $20 "I can't believe how cheap it was" to the $250.00 "OMG that's one expensive air filter!" We found what is probably what you would expect to find, the more expensive air filters flowed a lot more air than the cheap counterfeits however what was surprising was the cheap, dare I say it, "high performance" air filters generally flowed less air then the original stock air filter, ouch!
I'm not suggesting anyone go buy a $250 air cleaner and in many states or countries EPA restrictions don't allow for open air filters at all, however a good quality filter such as or similar to the K&N original replacement air filters, recommend as a good choice I would, as Yoda would put it.
Finally and briefly be careful of oil on filters, particularly on the inner side as we had some problems with the oil contaminating the hot wire on some air flow metres causing them to give wrong readings or fail all together.
You guessed it, change as per "the vehicle manufacturer's guidelines". However, fuel filters are quite often not changed due to the additional cost of a service, many are quite expensive, or because they can be downright dam hard to remove given where their mounted on some vehicles.
Fortunately and in most cases, a dirty or blocked fuel filter will cause a vehicle to surge in power, it is then driven into a workshop suspecting the humble turbocharger to be the culprit yet again, the "dirty fuel filter" is soon diagnosed and replaced after a fuel flow test and the owner is reminded to change the fuel filter more frequently until it comes back in again a few months later with the owner complaining about a surge in power and suspects the turbocharger. The word yoyo comes to mind!
Unfortunately on a more serious note, what can and does happen on occasion is the fuel filter may only be partially blocked allowing just enough fuel through for the engine to run properly or even feel like it has more power than normal and indeed it does have more power, awesome. This phenomenon in power increase is due to the engine running a leaner air/fuel ratio but unbeknown to the owner, whom can't hear the loud "pinging" from his engine as the sound system is set to120 db, is the fuel in the combustion chamber is pre-igniting due to excessive temperatures causing hot spots. They say the fastest a car will go is when it's at its leanest which is just a split second before a piston melts.