I have a 2001 SAAB 9-3. I was told that I should use a high octane fuel...that it would extend the life of the turbo. Is this true?
I would suggest checking the owners manual to see what Sabb requires for a minimum octane fuel.It should be 93 octane for your motor.That being said higher octane fuel will not help the turbo last longer.Octane ratings are a measure of the fuels ability to resist engine knock.Engine knock is caused by fuel ignition with the piston in the incorrect position.Engine knock will cause engine damage and shorten it's life but won't effect the turbo.What you can do to increase the turbo's life is change the oil regularly and allow the engine to idle for a minute or two after highway speed driving.This allows the turbo to slow down while engine oil is still being circulated through the turbo's bearings.
mikes is right: the octane is required for the engine, not the turbocharger on it's own. Said another way, the requirement for higher octane is a consequence of having a turbocharged motor vs. a normally aspirated one.
We've discussed some of the associated issues before. Here is some relevant discussion on the subject: