Diesel v petrol

[Triple-S]

Having heard today's news that plans are afoot to ban diesel cars from London, as Paris etc has done, can any experts amongst us tell me if diesel fumes are more dangerous than petrol. They talk of high parts per million of soot affecting the health of Londoners, but on other occasions say that petrol cars emit so much pollution the planet is suffering. Surely car manufacturers have chemists who were consulted before the market was saturated with diesel cars, but if so lorries and buses are so much larger they MUST be major polluters yet there was no mention of banning them.
As for the future, bring on fuel cell development and stop playing with silent death - the expensive-to-make and limited-range electric car.

Paul

[Brendan W]

Expert opinion seems to change with time. It's not so long ago that diesels were the CO2 saviours. Now they are the demons. I think their days are numbered. The complexity and fuel penalty from the E4 engines onwards has shifted the balance decidedly in favour of petrol. Many countries enjoy favourable tax treatment on diesel fuel and that is only a stroke of a pen away from disappearing. VW haven't done diesels any favours and that event may well the the straw the broke the camel's back.
Lorries and buses in an urban setting are taking the huge advantage diesel has at part load. It's also a lot safer to store and handle in bus depots.
They are producers of particulates and are strongly implicated in respiratory problems. Asthma in the young is a silent epidemic and current opinion is laying the blame on particulates from diesel and coal.
I think my next car will be petrol. Although at the rate it's lasting there could be more interesting choices by that time.
I believe Paris has already or intends to ban pre 2000 motorcycles from the city. Anything without a closed loop cat fuelling system seems to be on the radar as well.

[Harvey1512]

There does seem to be confusion and a lack of clarity over this. Not helped by govts focusing the car tax system in a particular way. The cost of fuel has also pushed us into wanting economical cars, not unreasonable. I'm aiming for 50+ on my next family lugger and no petrol car can do that. Maybe I have to change my outlook but how about govt put 20p extra on diesel and take the same off petrol. We can then adjust thinking so that 40mpg in a petrol is better than 50mpg in a diesel.

[Triple-S]

Here here Harvey, although I never even considered a diesel car as several parts were more expensive like for like on my sons diesel Escort, d-i-y maintenance was more difficult and that smell....
When I needed economy for one job I bought a moped...... Otherwise I don't give it any thoughts at all - it costs what it costs, and if I can't afford anything don't blame it on the price of fuel, just my economic position on the planet.
Only thing I will say: my old Morris Minor's exhaust stinks far more than my Volvo 240 ever did, so technology has moved on for the better.

Paul

[Daim]

Both engines cause fumes, which are unhealthy. Petrols cause mostly COx and diesels NOx.

Now, COx is easier to clean, with normal 3-way catalytic converters. Most modern (non-directin-jection) petrols will produse next to no NOx, next to no COx and very little Hx emissions. Direct injection engines emitt soot like diesels do and also produce NOx (due to the combustion methode and non homogenous mixture. This causes fumes and soot.

Diesels VAN be clean, it is a CAN but not ARE. To make a diesel really clean, it requires a lot of parts and fuel additives as well as fluids. A diesel will NEVER be as clean as a petrol. The only advantage of a diesel (mainstream engine design, no special small series constructions) is that it uses less fuel than equally powerful engines.

Fact is, that diesels emit more fumes, have worse emissions and cost more to service and keep healthy.

In my ooinion: on heavy goods haulers which stay away from cities should run on diesel. Busses can run on CNG/LNG. Trains are in cities mostly eletrical. Smaller delivery trucks (UPS, DHL, FedEx, Royal Mail, ...) can also run on CNG/LNG. There are a lot of ways to get diesels out of cities.

Many German cities are considering blocking diesels out of them too... Since Bremen has concerted most of the taxifleet to American V8s on LPG the air smells better. We have hybrid busses and the first LNG busses are being tested.

The days of diesels in personal cars will soon be over...

[The Thong]

Lets ban Diesel cars in London so we can build another runway at Heathrow.... Robbing Peter to pay Paul.

[DaveNP]

Declaration- As an HGV driver I do have a vested interest and I'm being sarcastic,

Let's ban all diesel HGV's from London, something like the current LEZ which stretches more or less to the M25 should do it. We can then replace each truck with 10 or 20 petrol vans, if we can build the vans in the UK we will boost manufacturing and the extra drivers will further boost employment, I'm sure no one will mind the hundreds of vans blocking the roads and the extra fumes from all of those engines will be petrol fumes so they'll be as healthy as menthol cigarettes, the cost of all this extra logistics will happily be absorbed by Londoners as we all know they earn masses more than the rest of the country.

Now being serious,
Any vehicle burning fossil fuels is going to emit pollutants, some more than others. The problem is differentiating between them, petrol used to be the devil's fuel because of the lead so we went to diesel with more mpg and no lead, now diesel is emitting soot so it's back to petrol. To my mind it's more symptomatic of poor government vacillating between populist causes rather than sound policy based on science. Ultimately we need to move to cleaner vehicles but I don't foresee a time when large amounts of goods can be delivered to your local supermarket in a totally green way.

[I-S]

Ultimately the problems stem from the fact that politicians are mostly not scientists nor have any kind of science or technology background.

This then means that they are legislating on matters that they simply do not understand.

In my professional life I keep being asked to produce figures for management and customer reps about error rates in coin handling equipment. They want a simple number - 1 in 10000 coins will be misidentified, misrouted, jam, or whatever. They are never satisfied with the answer "It's not that simple" - in this case it depends on the specific coin, the mode of operation, fill levels, etc. There's no headline "1-in" figure that means anything.

Sadly, that's exactly what government does - they wanted a figure of how "bad" an engine was for the environment, and the figure they chose was CO2 g/km. Diesels are lower in CO2 output per kilometer than petrols are, so we were all forced into diesels because of government policy.

And now it swings back the other way. There's jumping on the bandwagon of "ban diesel" all over the place, when in fact the emissions of Euro 6 diesel and petrol vehicles are pretty much indistinguishable. To now make diesel the bogeyman is blinkered and populist.

Tier	   Date	         CO   	THC	NMHC	NOx	HC+NOx	PM	PN [#/km]
Diesel
Euro 1†	July 1992	2.72 (3.16)	-	-	-	0.97 (1.13)	0.14 (0.18)	-
Euro 2	January 1996	1.0	-	-	-	0.7	0.08	-
Euro 3	January 2000	0.64	-	-	0.50	0.56	0.05	-
Euro 4	January 2005	0.50	-	-	0.25	0.30	0.025	-
Euro 5a	September 2009	0.50	-	-	0.180	0.230	0.005	-
Euro 5b	September 2011	0.50	-	-	0.180	0.230	0.005	6×1011
Euro 6	September 2014	0.50	-	-	0.080	0.170	0.005	6×1011
Petrol (Gasoline)
Euro 1†	July 1992	2.72 (3.16)	-	-	-	0.97 (1.13)	-	-
Euro 2	January 1996	2.2	-	-	-	0.5	-	-
Euro 3	January 2000	2.3	0.20	-	0.15	-	-	-
Euro 4	January 2005	1.0	0.10	-	0.08	-	-	-
Euro 5	September 2009	1.0	0.10	0.068	0.060	-	0.005**	-
Euro 6	September 2014	1.0	0.10	0.068	0.060	-	0.005**	6×1011***

Ultimately, it boils down to this:

If you burn fuel that has sulphur in it, you will get Sulphur Dioxide.
If you burn hydrocarbon fuel in an non-stoichiometric manner you will get CO and C (particulate soot) in addition to CO2.
If you burn fuel in air (that contains abundant nitrogen and oxygen) you will get some NOx

These things can be reduced and carefully controlled and that's what various emissions standards have done. However, they will not be eliminated completely.

Perhaps what we should learn from this is that combusting fuel is the common factor?

[Spike56]

Presumably once diesel engines are history, and the greenhouse gasses have built up, due to the 1000s of replacement petrol engines, there will be a call to ban petrol burners. Or perhaps cars with more than 3 cylinders?

Anyone for a Peugeot/Toyota/Citroen?

[Bungo]

Ban capitalism, that would clean up ALL the environment
Problem is we are too addicted .