Diesel Scrappage Scheme

james n posted:

Difficult to beat the low end shove of a nice torquey Diesel engine for everyday driving. I'm hanging onto mine for a while yet while waiting for the Gov to decide which way they are going with Diesel and what happens with Electric. Big take up of electric will mean some interesting challenges for the grid - interesting times ahead. 

I had a small Honda CRZ petrol hybrid that very much mimicked that effect. The small battery (charged purely by the engine during deceleration/braking) would give extra boost low in rev range and the petrol would then be delivering more torque as revs rose and boost fell off. It was no flying machine but  it was effective and a really nice thing to drive and own-yet sales appear to have been weak as I hardly ever saw another one. Struck me as an excellent compromise at this price/performance level and a good example of how a mild hybrid added to driving pleasure not just economy.

As the owner of a three cars, a small capacity petrol turbo, a 2.0 turbodiesel and a (classic) 3.0 V8 I'm happy to say they all have their qualities and very much fit their roles. The latter produces a whiff more C02 mind you!

Bruce

Derek Wright posted:

Can the particulates be filtered out of the air, can technology be developed to clean the polluted air in the cities?

Our Victorian ancestors planted Plane trees throughout London to absorb pollutants. The bark, which readily  falls off, takes the pollutants with it. I don't know if this would work with diesel pollutants or if it could cope with the quantities generated.

Derek Wright posted:

Can the particulates be filtered out of the air, can technology be developed to clean the polluted air in the cities?

Hi Derek,
Diesel particulates are very effectively filtered out by a particulate filter called a DPF.  

Gasoline particulates are much, much finer, so are harder to trap the same way.  However, gasoline particulate filters, or GPFs, are on their way for most developed markets in the next 2-5 years.

Nitros oxides can be (and are) controlled in 2 ways.  First, by making sure that the flame inside the engine doesn't burn too hot, as it is the peak flame temperature that allows NOx to form from atmospheric nitrogen and atmospheric oxygen.  Many engines today now recycle some of their own exhaust gas.  This reduces the quality of the air in the engine, so lowering the flame temperature below the threshold level and preventing NOx formation.  Second, manufacturers put a large, catalyst coated, ceramic filter in the exhaust, which then traps or reduces the NOx passing through.  One is called a Lean NOx Trap, or LNT.  The more common and effective one is called Selective Catalytic Reduction, or SCR.  With SCR, a small quantity of injected ammonia (NH3) reacts with the NOx in the exhaust, converting NH3 and NOx into steam and nitrogen.  The SCR system is very (i.e. typically 90%++) effective.

The best way to take away Sulphur oxides is to take the sulphur out of the fuel, hence low sulphur fuel.  Sulphur tends to poison most exhaust catalysts, so has to be removed before it reaches the engine.

Hope this helps, FT 

I think there is always more that can done as FT sugggests - but it will get to be a point of diminishing returns - just like with hifi. The step wise change will be with fuel and usage change - and possibly diesel / electric hybrids.

But currently the key differences between petrol and diesel Euro 6 is that diesel produces 50% of the the CO compared to petrol per km  and 33% more  NOx per km (i.e. 0.08 mg/km compared 0.06 mg/km). With NOx this is a step wise improvement for diesel over Euro 5

A good summary here from last summer:  http://www.theicct.org/sites/d...briefing_jun2016.pdf

S

Fuel can be improved, problem is it has a price penalty & gets into limitations for use in existing engines.  As I understand it,  with tighter spec's based around existing fuel standards coupled to developments/advancements in engine & exhaust technology,  the biggest bang for buck is in advancements in the engine.   

In my experience the quality of fuel at the pump is a real problem & I'm not talking UK, EU or US.  Outside those areas its very easy (common) to find fuel that bears no resemblance to what you & I know as petrol or diesel.   My old company had fuel attributable failures that were easily identifiable by country/region.  We had problems enough with Euro-2 engines,  but those problems turned to nightmare levels when we moved to Euro-4;  MTBF with fuel attributable causes changed by a factor of 3 between Euro-2 & Euro-4,  but by a factor of >10 comparing failures between EU & 'other' regions.     I have every sympathy with the engine manufacturers,  the drive for clean air in Europe is all well & good & pushes engine advancements,  but these advancements do not work in other regions were fuel is poor,   & it's ironic that these regions have 'normal' air pollution levels that would take us back to the industrial revolution.

There's some really interesting knowledge being shared here and I'm learning a lot. Keep it coming guys. I may buy another diesel yet.

Talking of fuel quality, I know it can fall outside Europe but even within I'm cautious about brand. I almost always buy Shell and have even persuaded myself that the car engine runs more smoothly if I fill it with the premium grade diesel (I have Merc C220D and the diesel power plant is a bit agricultural).  However, prior to that I used to run an E-class with a lovely 3.0V6 diesel. One day I was seduced by some money-off vouchers at out local Tesco and filled it with Tesco branded diesel.  Bl**dly hell, didn't I regret it! The engine ran rough until the whole tank (80 ltrs) was exhausted. Once replenished with Shell it immediately returned to running a sweet-as-a-nut.  Never again will I buy 'cheap' fuel.

Clay Bingham posted:

Friends

Diesel for passenger vehicles is dead....period. Never a big seller here in the US (>1.5% of the light vehicle market) the recent VW cheating scandal will end up being the final nail in the coffin. On top of that, it turns out that most manufacturers (BMW & Mercedes being the exceptions) haven't been meeting diesel standards in the EU either. They haven't been caught because the EU allows manufacturers to contract for their own testing. Scary information for those of you breathing in Europe. The move now will be solidly, electric, hybrid, and enhanced petro engines. Five years or so from now I doubt you'll be able to buy a new diesel car in the major markets of China, U.S. and Europe.

 

I don't think the diesel market is totally dead in the U.S. as General Motors  will offer a 1.6L turbo diesel for the Chevrolet Cruze in 2018. This diesel engine have been homologated and meet emissions for the U.S. 

MDS posted:

There's some really interesting knowledge being shared here and I'm learning a lot. Keep it coming guys. I may buy another diesel yet.

Talking of fuel quality ...... seduced by some money-off vouchers at out local Tesco and filled it with Tesco branded diesel.  Bl**dly hell, didn't I regret it! The engine ran rough until the whole tank (80 ltrs) was exhausted. Once replenished with Shell it immediately returned to running a sweet-as-a-nut.  Never again will I buy 'cheap' fuel.

..........  really, you cannot be serious !!!!  the next step is a bit techno babble'ish & it might end up longer than an ethernet cable thread.  

Re your Tesco fuel,  this is what I had in mind in my previous posts   " .......  with tighter spec's based around existing fuel standards"     Problem is although the fuel specs are quite specific, there are very few compliance checks,  what is the cetane number, what additives,   what's the biomass ratio  & the important bio-diesel question  .........  how old is it. 

cat345 posted:
Clay Bingham posted:

Friends

Diesel for passenger vehicles is dead....period. Never a big seller here in the US (>1.5% of the light vehicle market) the recent VW cheating scandal will end up being the final nail in the coffin. On top of that, it turns out that most manufacturers (BMW & Mercedes being the exceptions) haven't been meeting diesel standards in the EU either. They haven't been caught because the EU allows manufacturers to contract for their own testing. Scary information for those of you breathing in Europe. The move now will be solidly, electric, hybrid, and enhanced petro engines. Five years or so from now I doubt you'll be able to buy a new diesel car in the major markets of China, U.S. and Europe.

 

I don't think the diesel market is totally dead in the U.S. as General Motors  will offer a 1.6L turbo diesel for the Chevrolet Cruze in 2018. This diesel engine have been homologated and meet emissions for the U.S. 

Cat

It is true that GM talk about the existing and future Cruz diesels. They also mention a Cadillac diesel. But I think what your seeing here is an interim fix to enhance GM's fleet wide mileage in alignment with tightening federal standards. They already market a Cruze diesel but sell very few and as I noted above diesels are still less than 1.5% of the U.S. car market. And that figure is from 2015 before the VW disaster. Of course, its my opinion only and time will tell. Are you going diesel ?

 

Cheers

MDS posted:

There's some really interesting knowledge being shared here and I'm learning a lot. Keep it coming guys. I may buy another diesel yet.

Talking of fuel quality, I know it can fall outside Europe but even within I'm cautious about brand. I almost always buy Shell and have even persuaded myself that the car engine runs more smoothly if I fill it with the premium grade diesel (I have Merc C220D and the diesel power plant is a bit agricultural).  However, prior to that I used to run an E-class with a lovely 3.0V6 diesel. One day I was seduced by some money-off vouchers at out local Tesco and filled it with Tesco branded diesel.  Bl**dly hell, didn't I regret it! The engine ran rough until the whole tank (80 ltrs) was exhausted. Once replenished with Shell it immediately returned to running a sweet-as-a-nut.  Never again will I buy 'cheap' fuel.

Mike, same here. I always buy BP or Shell. And I always buy their premium Grade. I would never buy a supermarket brand. Even with (say) BP's regular v premium I find the mileage improvement justifies the extra cost, but I am convinced that it enables our cars, both petrol and diesel, to perform more smoothly. I normally get between 16k-18k service intervals on the C220 cdi.

Our family business morphed from Haulage --> second-hand cars --> filling stations. The filling stations included BP, Shell, Esso. I felt all these were "good" fuels.

Shelf-life is important, but I use mine so rapidly that a tankful never lasts more that a couple of weeks. Heck, I even use the petrol in the lawnmower before I store it for the winter, just to make sure I use a fresh supply in spring.

I must admit I thought there was a little controvesy with some of the premium fuels because of the extra additives contained - such as with Shell- and the additional emmisions they produced from the additives... perhaps this info is a couple of years old now... but I try and keep clear of them if I can unless it is the only fuel left which is not that unusual around these parts. Also on my BMW3 efficient dynamics - with average 68 miles to the gallon (119g CO2 per km)  .. I find my consumption increases slightly with the premium fuels and the performance dips a little ... it must be a synergy thing.. I tend to use regular Shell or BP diesel.

I've found premium diesel to be very engine dependant.   My BMW's were/are 50/50 on economy difference so I stick with the regular BP & Shell.  When I had MB's the premium grade got the 'promised' mileage,  but at that time the fuel was changing to ultra low sulphur so it might have been a combination effect.   Re additives;  its my understanding its a general purpose mix to not only clean the engine & optimise nozzle performance (NB with a dirty engine it takes a few tankfuls to take effect)  but also to help prolong fuel shelf life (important with bio content)  These additives might work better with (e.g.) multi-nozzle injectors,  but not for common rail stage injectors (NB: repeat e.g.) .......... this area is suck-it-&-see IMO. 

I have recently bought a diesel from choice.  I have yet to encounter a petrol capable of 70mpg with climate control, sat nav, stereo and lights running.  Most of my driving is on A roads and not around town/city.  The figure quoted by the manufacturer for mpg is not miles off.  It is wonderfully quiet and refined and a joy to drive.  If we all chose electric, think how many power stations we would need to build!

Clay Bingham posted:
cat345 posted:
Clay Bingham posted:

Friends

Diesel for passenger vehicles is dead....period. Never a big seller here in the US (>1.5% of the light vehicle market) the recent VW cheating scandal will end up being the final nail in the coffin. On top of that, it turns out that most manufacturers (BMW & Mercedes being the exceptions) haven't been meeting diesel standards in the EU either. They haven't been caught because the EU allows manufacturers to contract for their own testing. Scary information for those of you breathing in Europe. The move now will be solidly, electric, hybrid, and enhanced petro engines. Five years or so from now I doubt you'll be able to buy a new diesel car in the major markets of China, U.S. and Europe.

 

I don't think the diesel market is totally dead in the U.S. as General Motors  will offer a 1.6L turbo diesel for the Chevrolet Cruze in 2018. This diesel engine have been homologated and meet emissions for the U.S. 

Cat

It is true that GM talk about the existing and future Cruz diesels. They also mention a Cadillac diesel. But I think what your seeing here is an interim fix to enhance GM's fleet wide mileage in alignment with tightening federal standards. They already market a Cruze diesel but sell very few and as I noted above diesels are still less than 1.5% of the U.S. car market. And that figure is from 2015 before the VW disaster. Of course, its my opinion only and time will tell. Are you going diesel ?

 

Cheers

Clay, I own a 2015 Golf diesel with the AdBlue tank and I was disappointed to know VW do not plan to offer diesel cars anymore in US and Canada. I drive around 30,000 km a year and  just love it's fuel economy. Not ready to go electric before autonomy gets you at least 500 km with many fast charging stations everywhere.  The 2017 eGolf is a joke with a 200 km autonomy unless you own another petrol or diesel car for long distances.

Oh, branded, premium branded and supermarket fuels.  A tricky area indeed in which to generalise.  Even more so if one tries to make comparisons between different countries.

The International Council on Clean Transportation, or ICCT, publishes a number of excellent reports in the whole area of fuel quality, fuel economy and emissions.  It is an acknowledged international reference, so authoritative if a bit hard work to read at times.  Governments, the automotive and oil industries all use ICCT as a reference.

Let's make a start with gasoline/petrol in the EU.  There is an agreed standard for pump gasoline sold in the EU.  It is EN 590:2009 and was brought in with Euro 5 emissions standards to control a number of variables in the make up of the fuel.  Neither gasoline nor Diesel are a single molecule or compound.  They are both a blend of a range of hydrocarbon molecules, so the standard puts boundaries around the range of molecules that are permitted in the fuel.

First, the good news.  All petrol sold in the EU must meet this minimum standard.  All modern petrol engines for cars are also developed to run on this standard fuel, unless the car manufacturer explicitly says that a higher grade is needed.  These exceptions are normally very high performance engines used in sports cars etc.  Hence, supermarket and branded petrols all meet this minimum standard.  On the garage forecourts, this is often called 95RON petrol or premium unleaded.

However, there are a range of higher performance petrols, often called super unleaded, V-Power, Momentum, Ultimate etc.  

The various super unleaded fuels meet EN 590:2009 but also have certain enhancements in them.  The most notable is something called a higher octane rating or RON number.  Instead of being 95RON, they can be anywhere between 97RON and 100RON, though 102RON can be available from specialists (often at motor racing circuits).  The RON number is a measure of how hot and hard you can squeeze the fuel/air mixture before it detonates or knocks without being set off by a spark.  As detonation or knock are effectively an uncontrolled explosion inside the engine, so highly undesirable, a high octane rating or RON number is a good thing.  Modern turbocharged/supercharged petrol engines are designed to run close to the knock limit, so the higher the RON number, the happier your turbo petrol engine will be.

Some manufacturers take standard petrol, then add a dose of octane improvers to raise the RON number.  Shell used to do this with V-Power.  Others such as BP specially formulated a higher grade of fuel to meet the higher octane number.  High performance, turbocharged petrol engines like a high RON number.  The benefit comes in one of 2 ways: either the engine will produce more torque/power from the fuel if you drive it harder, or the engine will run in a slightly more efficient way if your driving style remains the same.  So the benefit of higher RON depends on how you choose to drive.

Then, there are a range of other additives that go into the super petrols.  These include detergents to "clean" the fuel injector nozzles, anti-bacterial agents to stop bio-fuel bugs from growing in the fuel tank/pipes/pumps to stabilisers that help to keep bio-ethanol from evaporating from the fuel.  There are a number of other additives as well.

Branded fuels tend to have these additive packs but supermarket fuels normally don't.  The supermarkets go for lowest cost so that they can sell at lowest price.  So with petrol, you can choose whether you want the standard supermarket fuels or the higher level of performance & protection that comes with some of the branded fuels.  Other than the performance/economy benefit of a higher octane fuel in turbocharged engines, most users are unlikely to notice much benefit from branded petrol.

Diesel is a very different story.  However, as this is already a very long post.  I'll stop at this point for now.

Hope this helps at least the petrolheads!  FT

Mike & Simon - I also run a BMW diesel estate - in this case with a 3 litre 6 cylinder turbo diesel engine - and I note that it specifically warns against using anything other than regular diesel - i.e. nothing with additives. While I mainly stick to regular diesel from the majors, I have tried some of their so-called "super diesels" a couple of times to see whether it made any difference. It made none that I could really tell, and consumption remained pretty much the same.  Conclusion: probably a waste of money in this instance.  Maybe a longer term use might make more of a difference, but I'm mindful of the warning around the fuel filler...

As for the diesel engine itself, it's a lovely thing - it seems ideal for normal road use really, with huge torque when you want it, surprisingly quick acceleration, and a sort of effortless quality regardless of gear. It's surprisingly refined and tuneful too, the extra cylinders make it much nicer than smaller versions, which sound gruff and agricultural by comparison.  The bigger engine does mean that economy suffers a bit, but over the last 10,000 miles of mixed city (london), motorway and country lane driving it has  settled on a 43mpg average, which isn't bad for what is quite a powerful and quick car.  Under similar driving conditions the petrol equivalent would probably struggle to crack 30mpg - my last BMW 6 cylinder petrol, deemed highly efficient for its day in the '90s, often struggled to better 23mpg...

It's difficult to consider going back to petrol after driving behind such a wonderful diesel engine as this.

Hi Richard,
A confusing picture, isn't it!  

My current BMW 6 cylinder petrol is now delivering 36mpg.  Not 43mpg for sure but it is getting closer and the fuel is also a little cheaper.  The latest turbocharged, direct injection, petrol engines are also being developed to deliver the same effortless, low end grunt that turbo Diesels offer.  The car makers have to do this because the want the engines to spend most of their lives running in the 1200-2000rpm range where fuel economy is highest.

Having tried a BMW 330D, a 335D and a 340i, the 2 stage turbocharged 335D is the fastest.  However, we much prefer the smoother, sweeter sound of the 33OD and the way that it delivers its performance.  The 335D is noticeably more rapid, yet the 330D is somehow more enjoyable.  The rear wheel drive version of the 330D also communicates more life through the steering wheel than the relatively inert (yet safer and grippier) 4 wheel drive of the 335D.  Very much a matter of personal preference though.  The 340i uses the most fuel, yet sings the sweetest tune while it does so.

Best regards, FT  

The main reason for choosing super petrol is increased performance.  There should be a small fuel economy gain but not enough to compensate for the higher cost of the fuel.

Diesel is different.  The main reason for choosing a super Diesel is not performance.  It's about increased protection of the engine and its very expensive and complex after-treatment system (i.e. the exhaust catalysts).

In Europe, the Cetane rating of super Diesels is typically only 1 point higher than that of normal Diesel.  There is little if any direct performance gain to be had here.

Because Diesel engines are used in trucks, there can be an expectation that Diesel engines are rugged, tough, bomb-proof.  This is very much not the case.  For Diesel engines to work, the dimensional tolerances, clearances, surface finishes, loads and pressures are all much higher than in typical petrol engines.  

Then there is the matter of complexity.  A petrol engine is typically a relatively simple, inexpensive beast with a single exhaust catalyst.  A Diesel engine is more like a complex gas processing plant that happens to produce some power as a byproduct.  Instead of a single exhaust catalyst, a modern Diesel may typically have an oxidation catalyst followed by a particulate filter followed by a NOx filter and possibly an ammonia filter.  All of these various filters have to be kept working in their own working temperature range in order to function.  There will also be at least 1 or possibly 2 different routes to recirculate exhaust gas back into the air intake - and the turbochargers have to cope with it too.

All of this is made possible by a sophisticated control system which keeps the engine running in an operating window which suits all the elements of the engine & its catalysts.

However, the engine wears with time and use, as do the various fuel injectors, catalysts and turbochargers.  And all the time, it is having to digest various impurities and unwanted contaminants.  These vary from bacterial bugs from bio-diesel to soot, ash, partially burned fuel and acidic water.  Over time, the engine and its exhaust system gradually bung up with this gunk unless you protect it.

What the super Diesels from the branded oil companies do is to help the Diesel engine  and its aftertreatment system get rid of the gunk, so preserving the performance.

One of the better known issues with Diesel cars is caused by only running the car for short journeys, especially when using basic diesel.  With a cold engine and a cold exhaust system, the particulate filter traps the soot but never warms up to the point where it can regenerate.  So it clogs up until the owner faces an eye watering bill for a new DPF.  Using super Diesel (at least 1 tank in 4 or so) and going on some longer runs of 20+ miles at higher speeds literally cleans the system out and preserves its performance.

The reality is even more complex & nuanced than this, but I hope this at least gives a flavour of what's going on.

Having said all of the above, I would caution against dumping in half a pint of "Diesel cleaner" additive into a fuel tank.  This type of product does contain aggressive additives in higher concentrations that will take the engine outside the carefully controlled operating window that the car maker knows is safe for both the engine and its exhaust system.

So in summary: use super petrols for performance but use branded super Diesels for protection of the engine and its exhaust system.  Aftermarket, DIY Diesel cleaning additives are best avoided.

Hope this helps.

Now, back to the turntable and some tunes, FT

FT, that's an excellent and most informative post, thank you.  

So from your post I can infer that using 'Super diesel" is OK and not the same as using a separate additive. Luckily, most of my journeys in the Bimmer are over 50 miles and a good mix of lane, main road, motorway and a bit of city, so I guess that the engine has a good opportunity to burn as cleanly as possible, but I shall now use "super diesel" every fourth fill up.

As mentioned earlier, I use either Shell V-Power or BP Ultimate. My main concern at the pump is whether to put petrol into the car or diesel !! The C Class (220 CDi) is diesel whilst the E Class (230TE) is petrol.

A few years back, I ran both cars for c.2,000 miles on Regular fuel, then a further 2,000 miles on V-Power/Ultimate. The fuel consumption on both cars was significantly better on the premium fuels and more than covered the extra cost per litre. I ran the cars for a few hundred miles after changing fuels in order to minimise running the tests on a mixed fuel.

Neither car has any warning not to use high octane fuel containing additives. So I have assumed that in addition to the fuel consumption benefit I am also benefitting from a cleaner fuel storage/delivery system, cleaner cylinders/pistons, and a cleaner catalytic/exhaust system. Both cars seem to run more smoothly on the more costly fuels.

Both cars have good acceleration performance, but since I get my adrenaline rush flying upside down whenever I wish, I tend to drive fairly steadily. About once a week, with the diesel, I do drive it "aggressively" in the vain hope that this will clean out the particulate filter a bit. This is probably pointless, but nevertheless a habit.

Nice post FT.   Despite BMW hinting that premium grades are not required,  I do fill with super diesel when I'm know I'm going on a series of longer journeys & especially so when I know the journey has hills where I can floor throttle as its these conditions that the cleaning agents really get to work,  motorways with a light throttle are not so effective.    A related side story; In my previous life we had customers with our diesel powered equipment that sometimes ran continuously 24/7 with very light loading & low(ish) RPM.  We had a programmable mode that forced engines to run a high load, high RPM cycle designed for the good of the engine. It could be programmed for doing this every 4, 8 or 12 hours,  unfortunately it also had a disable mode.  Normal use engines would be 'worn out' typically at 40,000 hours or greater.   Customers on very long slow running cycles & especially those that disabled the forced high speed mode rarely made it to 20,000 hours.   My message is give your diesel a bit of wellie once in a while.

Mike-B posted:

Nice post FT.   Despite BMW hinting that premium grades are not required,  I do fill with super diesel when I'm know I'm going on a series of longer journeys & especially so when I know the journey has hills where I can floor throttle as its these conditions that the cleaning agents really get to work,  motorways with a light throttle are not so effective.    A related side story; In my previous life we had customers with our diesel powered equipment that sometimes ran continuously 24/7 with very light loading & low(ish) RPM.  We had a programmable mode that forced engines to run a high load, high RPM cycle designed for the good of the engine. It could be programmed for doing this every 4, 8 or 12 hours,  unfortunately it also had a disable mode.  Normal use engines would be 'worn out' typically at 40,000 hours or greater.   Customers on very long slow running cycles & especially those that disabled the forced high speed mode rarely made it to 20,000 hours.   My message is give your diesel a bit of wellie once in a while.

Ha !, looks like my once-a-week thrash might be doing more good than I thought !

Thanks Mike.

Mike, Don, Richard,

It's tough, I know, but someone has to give those Diesels a thrashing from time to time 

Just allow time to warm up the engine oil (this can easily take 5+ miles) before you do so and then be gentle for the last mile of your journey, so that the turbocharger & exhaust manifold cool down a bit.  In between lies the opportunity for fun.

Best regards, FT

Mike-B posted:

Nice post FT.   Despite BMW hinting that premium grades are not required,  I do fill with super diesel when I'm know I'm going on a series of longer journeys & especially so when I know the journey has hills where I can floor throttle as its these conditions that the cleaning agents really get to work,  motorways with a light throttle are not so effective.    A related side story; In my previous life we had customers with our diesel powered equipment that sometimes ran continuously 24/7 with very light loading & low(ish) RPM.  We had a programmable mode that forced engines to run a high load, high RPM cycle designed for the good of the engine. It could be programmed for doing this every 4, 8 or 12 hours,  unfortunately it also had a disable mode.  Normal use engines would be 'worn out' typically at 40,000 hours or greater.   Customers on very long slow running cycles & especially those that disabled the forced high speed mode rarely made it to 20,000 hours.   My message is give your diesel a bit of wellie once in a while.

Confims what a trusted service mechanic once suggested to me.

FT i also enjoyed and learnt from your post today - your point of diesel engine wear is interesting - and as diesel engines tend to operate over significantly longer mileage lifespans than petrol this is probably quite relevant. Can you advise to what extent if any the UK MOT system assesses pollutants from ageing diesel engines?

PS Average consumption from East Suffolk to Swindon and return today 64 mpg - perhaps a little lower because of all the water on the road...?

Also last month bought a little petrol Skoda Citigo for family use around the local villages, coast and to town so as to avoid using the diesels for short trips i.e. <10~15 miles.. and its great fun - refreshing change from the big cars....

Simon-in-Suffolk posted:

FT i also enjoyed and learnt from your post today - your point of diesel engine wear is interesting - and as diesel engines tend to operate over significantly longer mileage lifespans than petrol this is probably quite relevant. Can you advise to what extent if any the UK MOT system assesses pollutants from ageing diesel engines?

PS Average consumption from East Suffolk to Swindon and return today 64 mpg - perhaps a little lower because of all the water on the road...?

Also last month bought a little petrol Skoda Citigo for family use around the local villages, coast and to town so as to avoid using the diesels for short trips i.e. <10~15 miles.. and its great fun - refreshing change from the big cars....

Simon, provided your vehicle is serviced in accordance with the manufacturer's guidelines you should achieve a fairly high mileage. One point to bear in mind is it is imperative that the correct specification of lubricating oils are used as these will be blended with certain additives which could include detergents these will most certainly be vehicle specific and go a long way in maintaining engine life and reliability.

Retired early a couple of years ago my last two company VW Passat diesels covered around 40,000 a year with a total mileage of 175,000 and 170,000 respectively the only major component change apart from a new DSG gearbox replaced under warranty was a new exhaust Catalyst changed on the first one it never failed internally just cracked around the connection joint ironically it failed whilst I was awaiting delivery of my new Passat.

Excellent posts from Mike and FT and as FT explained it's the short commute journeys than can be more detrimental to the longevity of the diesel engine and its associated exhaust gas treatment components whatever type they may be.

You should be able to find the MOT Emission test requirements on the VOSA website 

My current employer services my BMW and so I have every confidence it is maintained correctly, and correct and efficient tyres are also critical for low consumption.. perhaps often over looked?. It is the various increasing pollutants from ageing engines, especially diesels I am curious of.. and my suspicion is the MOT is somewhat behind the specifications of new engine requirements..which might loop us back to the OP.

My question regarding removing the "nasties" was more to do with the nasties that have pushed into the urban environment.

Is there a possibility that street located air conditioners could be placed in the streets to suck in the dirty air and blow out cleaner air.

Would it be possible to design such a device?

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