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    Could a bad turbo bearing on a car affect the fuel economy / MPG of said car ?

    thanks
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    It depends how knackered it is, short answer; Yes.

    Long answer;
    I assume your hearing police siren noises when you rev your engine, this is the calling card of a badly worn turbo bearing, the sound is caused by the compressor blades wiggling in there housing very slightly and scrapping against the wall of the turbo (these things are goijg around at about 20,000RPM). This will cause loss of boost pressure and will get worse until the turbo packs in completely (possibly resulting in a knackered engine). This loss of pressure will cause a flatspot in power at low to mid RPM as the turbo is spooling meaning your car will feel slow to react to throttle adjustment. However because your engine is tuned to run with positive inlet pressure it will continue to dump fuel into the cylinders as if all is well, this causes incomplete combustion as the fuel doesnt get enough air forced in through.the inlet to burn right resulting in you losing unburnt fuel out the back. In a diesel this also comes out as a plesent acrid black smoke, in a petrol it can also cause damage to your catalytic converter.
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    (Original post by I love life)
    Could a bad turbo bearing on a car affect the fuel economy / MPG of said car ?

    thanks
    Short answer - yes. The turbo on my Focus started to pack in and MPG went from 45 - 55 down to 20. We got rid straight away as a knackered turbo would have been about £1500 to replace and if it failed could have taken the engine with it. We now have a nice simple petrol engine. No silly turbos to complicate matters.

    Good luck!
 
 
 
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