Lets divide the scenarios into Highway and City and then analyse. Highway On highway runs , the general pattern of driving demands maximum from the turbo and the engine. Hence , the turbo gets pretty worked up. Now, turning it off instantly after a highway run is very bad practice and hence atleast a minute's idling is required . Mind you , a minute is the bare minimum. The time duration for which you have to idle is directly proportional to how hard you have been driving. Another commonly accepted way to avoid the minute or two's idling is - To drive sedately before reaching your destination / your intermediate stop. Although the distance for which you got to drive sedately is a topic for discussion , 2-3 kms is safe . That means , drive "off boost" ,i.e. at rpm's where the turbo does not start making boost till you reach the destination/intermediate stop. By this way , when you reach, ~30 secs of idling should do the trick. I personally prefer the 1-2 minute idling before shutdown and follow it religiously. City City driving provides us the opportunity to drive off boost, generally . By driving off boost we can expect better kmpl figures as well as lower temperatures at the turbo. Here again , both the above methods can be employed. But the idling method is the one which i would vote for everytime. That is when the Exhaust Gas Temperatures drop is high resulting in cooling of the turbo. Turbos can last lakhs of km's when cared for. If not then even 50,000 km's of poor driving practices can kill it. Whenever you see a turbo car emitting blue smoke , fried turbo seals are a probable cause. Due to improper driving practices. And lastly , if you find idling the engine for a minute or two as rather long , i suggest you google Turbo Timer . It keeps the car running for a pre set period of time. Upon reaching the destination , you can simply remove the key , lock the car and move. The Turbo Timer will switch the engine off only after the pre-set duration of time. Gurjinder.