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Noticed this in the 2022 Owner's Manual:

"After driving at freeway speeds or up a long hill, idle the engine at least 30 seconds before stopping it. Otherwise, the turbocharger could be damaged."

I'm curious if anyone has any insight into this? I don't like these kind of statements because they are so vague. For example, how LONG after driving highway speeds or going up a long hill?

If I drive to work, come off the interstate, and then navigate city streets for a few minutes, do I still need to worry about damaging the turbocharger if I don't idle for 30 seconds?

I half wonder if these kind of statements are for corner cases that can cause damage that they don't want to cover under the warranty, so they put an overly broad statement in the manual to cover their asses.
 

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I’m no mechanic, but from what I’ve read in the past this is to help cool the turbo down. Oil deposits (“coking”) can build up from the turbo getting really hot from harder driving then being shut off quickly and stopping the oil from circulating, so letting things cool off a bit can help mitigate that.

Does highway driving or driving up long hills fit in the “hard driving” category? Guess it depends if you’re sunday driving vs trying to outrun the cops. We drive up a long, steep hill (about 4 miles at 10% grade) to get home, so I let the engine idle for a few seconds after pulling into the garage. Even though there’s about half a mile of slow driving between the last of the uphill section to our driveway.
 

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22 CX 30 Turbo GT & 22 3 in Soul Red
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Not sure how they could prove you didn’t let your turbo cool down to deny a warranty claim.
But as a heavy equipment operator, yes you do need to let the turbos cool down AFTER a strenuous workout. You state you do some city streets after coming of the interstate, that’s fine, unless of course you are just nailing it on the interstate in 4th gear on a really hot day. The intention of the statement in the owners manual is for those types of people with that driving style, like climbing the Rocky Mountains to the summit then pulling over to the viewpoint and shutting it down.
Don’t worry too much about it, just be conscious of your situation when driving and act accordingly.
Enjoy.
 

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Either the coolant loop is designed to self-circulate after engine shut off, or there is a coolant pump that runs after shut off.
I'd wager that it's the former but it was never confirmed. I personally heed by the 30 second rule because the turbo does get super hot, as observed by opening the hood.
 

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It isn't an automated coolant loop at issue. It's flushing out all the super hot oil and circulating some that's much cooler; the engine has to run to do that. If the hot bearings can't get fresh oil, the oil that is not flushed will turn to coke which eventually builds up and wrecks the bearings.
 

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Either the coolant loop is designed to self-circulate after engine shut off, or there is a coolant pump that runs after shut off.
I'd wager that it's the former but it was never confirmed. I personally heed by the 30 second rule because the turbo does get super hot, as observed by opening the hood.
There are aftermarket products ("turbo timer") which you can buy which will do this for you. After your turn off your ignition, the timer will keep the engine running for a minute or two in order to keep the oil circulating before shutting off.
 

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The skyactiv turbo has coolant ports near where the bearings would be so it does play a part.
Even if there were some sort of additional coolant pump, once the engine is off, the oil isn't flowing through the turbo and if the turbo is redhot, the stagnant oil is going to cook inside the turbo.
It's like constantly stirring a soup to keep it from burning on the bottom. The oil has to keep circulating until after the turbo has cooled off.
 

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this is well known thing that I always did when drove my Alfa Romeo 156 1.9 JTD (turbo diesel). The meaning was to allow oil to coll down bearings after a run under the load. Another option was to drive with a very light load for the last five minutes to keep oil running, but turbo turning only slightly.
Those who didn't - suffered bearing failures. It was a well-known thing. Oil was boiled by the hot bearings and turned into gunk. Blocking intercooler, bearings were suffering lack of oil etc. Many turbos were killed by that... Major topic of discussion on Alfa Romeo forums.
Of course it was the design from 1998-2004, but I wouldn't be surprised if it is still important since turbos are going through crazy rpms

I guess it won't be very difficult to prove for Mazda if the system is full of coked oil.
 

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Unless you are hard on it or doing track days and shutting it down right away, a few minutes of light driving will suffice for most drivers.
 

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With todays synthetic oils and with how most people drive their cars day in and day out this just isn’t a huge issue. If you’re drag racing people at every stop light, constantly at WOT for long durations like a track day, or even some mountain driving up steep grades it would be Advisable to let the turbo cool off for a bit. Other then that you’ll be fine. Ive had 3 different turbo cars before this one and not once did I ever destroy a turbo from oil sludge build up. My WRX and legacy GT both clocked over 100k before I sold them on original turbos with no issues.
 
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