Turbocharger information that was a bit alarming...

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2005 Mazda3
Probably found in all the service manuals with a turbo just to cover themselves. Like others have mentioned this was common practice with turbo's through the 80's and even in the 90's it was common knowledge. I recall most of my friends installing "turbo timers" as well, basically when you turn the keys off the engine would stay on for a timed amount of time to let the oil and everything to continue to run and circulate and then shut off so you wouldn't have to sit there inside and wait. I'm sure lots of owners of turbo's in the 90's didn't follow this, the cars still survived but it wasn't good for the car, especially after hard driving.
 
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Pueblo county CO
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CX-5 Sport 16.5 6M
I remember reading the manual for a 1965 F250 truck with a small straight six (of course no turbo). It had a similar warning.
 

JPL

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2018 Mazda6, CX-9
They bury supposedly critical info in the manual that 95% of people don't read. Idling may have been common knowledge in sporty turbo cars of the '80's & '90's, but a large portion of the auto market is now turbo to decrease engine sizes. Who thinks crossover owners are cooling down their engines? When you're on a road trip, you gas up at stations immediately off the highway which means immediate shutdown. Thing is, you're likely not under boost when cruising on the highway. Only when passing and merging, so I don't think this is a issue.
 
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CX-9 GT 2019
I have a natural setup to test this for the last 7 years. I live on a hill and every time a get home its a steep uphill for half a mile. then 10 sec of a minor uphill and 10-20 sec of idle rolling and parking before i shut off the car.

It is naturally hard to break 30sec rule too badly because parking takes some time. However I’m on the edge or below 30sec most of the time.

All my turbo cars throughout those years never shown any signs of sludge or turbo issues. Old passat b6 had open filter and I’ve never seen any sludge with 7500mi intervals.

Next, 15 wrx was my precovid daily and i would estimate it did that routine at least 2k+ times. It has always been cobb stage1, so a bit hotter than stock. It is now at 75k miles and protuned, so even hotter. Only after protune i started to even think of idling a bit if i park too quickly.

Finally, my cx9 does the same for its 27k miles. However, I can't zip into the garage in it without some backing up, so it gets extra seconds.