We've got two diesel cars with manual gearboxes. The first is a Freelander 2, which is old enough to avoid having the dreaded DPF and doesn't have stop / start either. The other car is Golf 2.0 TDi, with the Bluemotion Technology stop / start system and a DPF.
In the Land Rover, you can't start the engine unless the clutch is fully depressed and I always depress it before switching off too. Not sure if does help to prolong DMF life, but one or two on here have suggested it does and I'm hoping that my smooth driving stlye will also help its longeveity a little!!
On the Golf, again the engine can't be started without the clutch being depressed and when I get to the end of a journey habit dictates that I depress the clutch prior to turning the engine off. However, the stop / start system cuts the engine at traffic lights if the clutch pedal is not depressed and the car is in neutral and restarts as soon as you start to depress the clutch, so these 'stops and starts' are happening when the clutch isn't depressed. Any thoughts on whether this is likely to impact of DMF life in the long run?
The stop /start system on the Golf is quite keen to shut the engine off at traffic lights, even if the engine is nowhere near normal operaring temperature. There is a set of lights around 1/2 mile from home and even in the depths of winter after a cold start, it will still switch off at the lights, after a journey of about 2 minutes. On really cold mornings, I tend to deactivate stop /start for the first couple of miles, as I can't help but feel that it's beneficial for the engine to get to normal temperature as quickly as possible and repeated cold starts can't do the DPF any good, as emissions of particulates are at pretty high levels after cold starts. To be fair, there have been no problems with the car (DPF or otherwise) in 10 months and almost 19,000 miles, but that could be because it gets a decent run each day. Are others likely to be contributing to the demise of their DPF if they allow the system to keep shutting off the engine when it's still cold?
Although there wan't room in the subject header, the other part of the car that could suffer with stop / start systems is the turbo. Where I leave the motorway on the way home, there's a short slip road with traffic lights at the top (always on red!) and I don't let the car stop itself, as I'm not convinced that the turbo will have spooled down before its oil supply is cut off. I guess another scenario that could damage turbos would be somebody participating in the traffic light grand prix and thrashing from one set of lights to the next, pulling up, engine shuts down and the turbo is still flying round at 10,000 rpm...
So, whilst stop / start technology may lead to better MPG (not entirely convinced) and does help to reduce BIK figures and thereby tax for company car users, is the reality that it's (potentially) bad news for DMFs, DPFs and turbos if the driver has little or no mechanical sympathy?
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