Lesson from a submarine engineer

[ashley karyl]

My father has had a 2006 Toyota Avensis T180 since new. It is a turbo diesel that has covered just 40,000 miles and we agreed recently I should keep it instead. A few days ago I drove about 15 miles followed by another car. The other driver is a recently arrived Ukrainian refugee, who was a submarine engineer in his younger days. 

When we arrived I switched off the engine as usual, however he kept his Renault turbo diesel idling for a couple minutes, saying it was important on a turbo diesel to avoid engine damage. After returning home I checked out the manual on the Avensis and sure enough it was there with wait times dependent on the top speed of driving. I have attached a couple jpg files with both start and stop information for anybody who is interested. 

My thought is whether this idling time is really necessary if you pull off a dual carriageway and then drive for a mile or two in town at 30mph before stopping. Is that adequate or should we still allow the engine to idle for a couple minutes before switching off? 

 

[Stivino]

I have that car too (2008).  I never let it run before I switch it off as the last couple of minutes to my house from the motorway are enough.  And, most of my driving is in town.

Some sporty cars have that feature built in.

[Bper]

I have a Auris 1.2 T and always allow a minute before pulling away from cold and the same when stopping.

Turbocharged engines do need to cool down before they are turned off. But in nearly all driving conditions, the engine does not reach temperatures that require a deliberate cooling-down period.

Switching off when the engine is very hot stops the circulation of oil. The layer of oil around the turbocharger bearings stop flowing and literally gets “burnt”. The black sludge that forms is not good for any engine.

In all other situations, even sustained high speed driving on motorways and A  roads, there is inevitably a period of low-speed driving before parking the car or switching off the engine. That is sufficient for the engine oil to cool to a level that will not damage the turbocharger bearings.

Also, always ensure that you are using the recommended grade and viscosity of engine oil for your turbocharged car.

[ashley karyl]

This is the first diesel I have ever driven or for that matter a turbo either. In the past, I have generally been inclined to start the engine and let it idle for 30 seconds before setting off from cold with other cars, so that the oils circulate. The Toyota manual specifically advises against this on the diesel and says it should be driven away immediately. 

This point about having to allow time for the turbo engine to cool down did interest me though, as I would hate to cause damage through lack of awareness. I actually wondered how much use the turbo gets if cruising in 6th gear at 1800 rpm. 

 

 

[TonyHSD]

This advice is true and highly recommended to follow on any turbo powered car no matter petrol or Diesel engine. However you need to let the car idling for a minute or two after a long motorway drive at high speeds 65+mph or after long uphill or longer hours of continuous driving. For short town trips up to 30 miles (30-60min) there is no need to do that. It is all about cooling down turbo shaft which spins at very high rpm and very hot gasses past through it. Once you drive for some minutes off the motorway upon your arrival the engine and turbo will be cooled off and you are good to switch off. 
Also waiting one to two minutes before driving off on cold starts is vital to maintain proper engine lubrication and extend its life. These steps are recommended for pretty much all internal combustion engines even hybrids. 👍

[Cyker]

It is not a bad habit to get in to, but 90% of the time unnecessary (Unless you literally live off a high-speed A-road like a friend of mine did ) because, as has been said, that slow crawl on the last part of the journey home is usually enough for it to cool down to safe levels.

The danger is things like motorway services, where you're ploughing along at 70mph and e.g. suddenly need to pee, so you jump into the next services, immediately shut the car off and leg it to the bathrooms while the turbo is cooking off the oil!

 

[Rhymes with Paris]

27 minutes ago, Cyker said:

It is not a bad habit to get in to, but 90% of the time unnecessary (Unless you literally live off a high-speed A-road like a friend of mine did ) because, as has been said, that slow crawl on the last part of the journey home is usually enough for it to cool down to safe levels.

The danger is things like motorway services, where you're ploughing along at 70mph and e.g. suddenly need to pee, so you jump into the next services, immediately shut the car off and leg it to the bathrooms while the turbo is cooking off the oil!

 

And the problem becomes more and more urgent the older you get.

Reminder to self : Do not replace my Yaris with a turbo engined motor.