The Naked Scientists

The Naked Scientists Forum

Author Topic: What is the difference between diesel fuel and petrol (gasoline)?  (Read 128274 times)

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Thank you for the welcome Lightarrow but I can agree with few if any of the points you make.
I don't know what a Sanity Department does but it clearly doesn't do much to do with engine emissions in the real world.
This clearly show that you are talking about another planet. Sanity departments (at least here in Italy!) are continuously studying, sampling, making conferences on this subject. If you don't believe what I say, we have nothing to discuss anylonger.
Maybe you sell diesel vehicles or you are pushing for it...
Studying, sampling and making conferences about what exactly? As you have clearly not studied or sampled much petrol emissions if you think they are safer than diesel ones.
It's not my opinion.
Quote
have you studied or sampled much of the emissions from the new "petrols that work like diesels but still have the most unreliable bit the High-tension ignition system" the FSI and other direct injection engines they produce NOX as well.
Pressures inside an FSI petrol engine are about 10 times lower than those in a corresponding common rail diesel. So NOx are much lower.
Quote
Diesel virtually eliminate their NOX with EGR (Exhaust Gas recirculation, in case your sampling and studying hasn't got that far).
You are dreaming. You don't even realize the difference in smell from a diesel engine exausts and a petrol engine. I studied and made chemistry and I can tell you the smell from diesel exausts means great amounts of NO2. If you don't believe it, make this simple experiment: dissolve a piece of metallic copper in nitric acid and observe the red smoke it forms; then remember the smell it has. Then look up a chemistry book looking for all the physical, chemical and tossicological properties of NO2.
Quote
I fear the Italian version of SANITY (I wonder if you mean Sanitary?) is way out of step with Audi, VW, BMW, GM, Ford, Citroen, Peugeot, Renault and even Errrrr FIAT who all see diesel as the only way of meeting both CO2 and air quality standards.
What car companies and governements told us are not what data analysis show...Furthermore, they make us focus our attention on the CO2 problem, instead of much worse problems. Do keep breathing particulates and NOx at these levels and we won't have to worry about dissolving poles, because we will all be ill before.
Quote
Alcohol is a dead end it is expensive and energy hungry to produce and wasteful of huge areas of land - much more land is needed to produce the same energy value of alcohol than of bio-diesel. It is also more dangerous and more difficult to store and more wasteful in use due to losses by evaporation.
Bio-diesel comes directly as liquid from trees? Making it needs energy too. Alcohol is not more volatile and more difficult to store than petrol.
Quote
However, Yes you are right on one point - if you can't see that and can't see past your clear and undoubted prejudices - you have nothing more to say on a matter you clearly have little relevant knowledge of.
And NO I do not sell diesels - I drive them with a clear conscience and the sooner I can drive anywhere using waste vegetable oil as fuel my conscience will be even clearer
Maybe your conscience, but not the air we all breathe, unfortunately.
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
I'll connect a pipe to my diesel exhaust and you connect one to your petrol exhaust and then breath it in for a few minutes - I'll have a cough (maybe)- you won't have a cough you'll have a funeral.

I repeat: petrol emissions kill instantly and there are millions of suicides (including a good friend of mine) to conclusively prove that.

Diesel emissions MAY kill in decades and even that hasn't been proved yet and neither you nor anybody else can produce one single person who can be conclusively proved to have died solely as a result of diesel exhaust fumes.

If that friend of mine had followed my advice and had a diesel car he might still be alive, he certainly wouldn't have died in his car.
 

Offline rosy

  • Neilep Level Member
  • ******
  • Posts: 1018
  • Chemistry
    • View Profile
As has been remarked in this and another thread, this forum thread has been linked from some BBC page somewhere... I don't know where, since no-one's posted the link.

This is rather unfortunate since this forum (being an entirely open discussion area) contains quite a lot of interesting and well argued material posted by individuals who have serious background knowledge or a good record in checking their facts, in response to questions about interesting areas or science and research. However, the diesel/petrol debate is sufficiently contentious (and enough people have a stake in terms of wanting to believe they've made the right choice of car) to fall prey to the not uncommon problem of people with Strongly Held Views shouting louder, longer and more often than those with a more measured viewpoint.

I can only remark, for the benefit of anyone who hadn't already grasped this fact, that all open discussion areas are only as informative as the people posting to them are informed. Some contributors are pretty reliable, and I shall cite Chris and Daveshorts as examples because I know both (and their trackrecords) fairly well, although this is by no means meant to cast aspersions on anyone else (or not anyone in particular).

For new vistors... the quality of debate on this thread is depressingly low, overendowed with ad hominem attacks, and not in my view (as a site regular) typical of this forum.. tho' it's not unheard of either.
Whilst I'm addressing any new visitors, I may as well point out that as well as the forum this site has a load of other content, including a lot of articles on various scientific topics and podcasts of the Naked Scientists radio show, neither of which are afflicted with underinformed rants.

(Apologies, I'm going to cross post this to the feedback thread too.)
 

Offline elegantlywasted

  • Hero Member
  • *****
  • Posts: 573
    • View Profile
    • Deviant Art
I'll connect a pipe to my diesel exhaust and you connect one to your petrol exhaust and then breath it in for a few minutes - I'll have a cough (maybe)- you won't have a cough you'll have a funeral.

I repeat: petrol emissions kill instantly and there are millions of suicides (including a good friend of mine) to conclusively prove that.

Diesel emissions MAY kill in decades and even that hasn't been proved yet and neither you nor anybody else can produce one single person who can be conclusively proved to have died solely as a result of diesel exhaust fumes.

If that friend of mine had followed my advice and had a diesel car he might still be alive, he certainly wouldn't have died in his car.


Uhh I have a small problem with the statement that petrol emissions kill "instantly"... Years ago, a friend of the family, on a bet (he was 8) put him mouth to a tail pipe of his fathers Ford while the car was running. Although he was terribly sick (nasty cough for months) and had some pretty nasty burns to his face, he isnt dead. Actually he plays for the farm team of an NHL hockey team... Definatly isn't dead, definatly now a professional athelete.
« Last Edit: 15/02/2007 22:04:01 by elegantlywasted »
 

Offline elegantlywasted

  • Hero Member
  • *****
  • Posts: 573
    • View Profile
    • Deviant Art
And rosy... excellent post.
 

Offline daveshorts

  • Moderator
  • Neilep Level Member
  • *****
  • Posts: 2583
  • Physics, Experiments
    • View Profile
    • http://www.chaosscience.org.uk
Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.

In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emmision annoyingly.
 

another_someone

  • Guest
Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.

In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emmision annoyingly.

CO2 is far less toxic than CO, but as far as I am aware it is still toxic (i.e. you will die sooner breathing in an atmosphere of CO2 than breathing in an inert atmosphere - e.g. N2 or He).
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
Here is the link to the BBC page with the link to this Topic.
http://www.bbc.co.uk/radio4/science/homeplanet_20070213.shtml [nofollow]
If you object to having this forum quoted in this way please take it up with the Producers of the Programme - "Pier Productions"



Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.

In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emission annoyingly.


Correct IF a catalyst is fully warmed up and working properly, the catalytic effect being temperature critical (that's why your car has to be fully warmed up for the MOT test). However that takes quite a while, much longer than most people think and in cold weather it can be 15 miles or so depending on driving conditions and until that happens a cat equipped car is actually pumping out more harmful emissions than a non cat equipped one because fitment of the cat causes it to run less efficiently - approx 10% worse.

CO is toxic it combines with something in the blood, Red Corpuscles maybe? and prevents them forming Oxyhaemoglobin  and making Carboxyhaemoglobin instead (perhaps any haematologist who reads this could verify/correct my recollections from schooldays).

CO2 is not toxic but inert (SFAIK) and would kill in just the same way as any inert atmosphere that did not contain any oxygen. It is the lack of oxygen that kills not the CO2 - it's how CO2 fire extinguishers works as well.

How ever little CO a modern fully warmed up catalyst equipped petrol engine produces it is still more than any diesel exhaust emits, as diesels always operate with an excess of Oxygen and CO can only form when there is a deficit of Oxygen (once again SFAIK).

Modern diesels operating on modern Ultra low sulphur diesel or even better totally sulphur free bio-diesel easily meet the same emission standards as catalyst equipped petrol engines whilst using much less fuel and producing much less CO2 and they do not need a Lambda sensor and all the inherently unreliable electronics associated  with it to do so.
Less fuel = Less emissions = Less trouble for the planet and all who live on it.
« Last Edit: 16/02/2007 00:04:29 by scanner »
 

Offline lightarrow

  • Neilep Level Member
  • ******
  • Posts: 4586
  • Thanked: 7 times
    • View Profile
Petrol engines do produce more carbon monoxide than a diesel and it was unfortunately a common way to commit suicide, however if your car has a catalytic converter fitted (anything newer than at least 20 years old) the platinum and palladium catalysts help oxygen in the exhaust gassed to oxidise the CO into CO2, and I think the  resulting exhaust is no longer very poisonous. Possibly the only way it could kill you is by a shortage of oxygen, but that is going to be quite a challenge.
In the UK an old car with not catalytic converter will fail it's MOT with 5% CO and one with a Converter will fail at 0.2%, apparently, and most cars will do a lot better than this. Possibly a problem if you tried to breath it directly, but will take at least 10 times longer than the hour or so it used to take. I can't find any figures for diesel CO emission annoyingly.
Correct IF a catalyst is fully warmed up and working properly, the catalytic effect being temperature critical (that's why your car has to be fully warmed up for the MOT test). However that takes quite a while, much longer than most people think and in cold weather it can be 15 miles or so depending on driving conditions and until that happens a cat equipped car is actually pumping out more harmful emissions than a non cat equipped one because fitment of the cat causes it to run less efficiently - approx 10% worse.
CO is toxic it combines with something in the blood, Red Corpuscles maybe? and prevents them forming Oxyhaemoglobin  and making Carboxyhaemoglobin instead (perhaps any haematologist who reads this could verify/correct my recollections from schooldays).
CO2 is not toxic but inert (SFAIK) and would kill in just the same way as any inert atmosphere that did not contain any oxygen. It is the lack of oxygen that kills not the CO2 - it's how CO2 fire extinguishers works as well.
How ever little CO a modern fully warmed up catalyst equipped petrol engine produces it is still more than any diesel exhaust emits, as diesels always operate with an excess of Oxygen and CO can only form when there is a deficit of Oxygen (once again SFAIK).
Modern diesels operating on modern Ultra low sulphur diesel or even better totally sulphur free bio-diesel easily meet the same emission standards as catalyst equipped petrol engines whilst using much less fuel and producing much less CO2 and they do not need a Lambda sensor and all the inherently unreliable electronics associated  with it to do so.
Less fuel = Less emissions = Less trouble for the planet and all who live on it.
Yes, catalized petrol engines produces CO before the catalitic exaust is hot; but diesel engines produces NO2 always. CO is extremely toxic, we all know; NO2 is extremely toxic AND carcinogenic; it also gives a combined effect with HC (uncombusted hydrocarbons).
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
Please supply a link to any information that NOX is carcinogenic as that is news to me and I have never heard it suggested anywhere else than in this forum.

In fact a google turns up this reference

Quote
   
How likely are nitrogen oxides to cause cancer?

The Department of Health and Human Services (DHHS), the International Agency for Research on Cancer (IARC), and the EPA have not classified nitrogen oxides for potential carcinogenicity.
that took all of 2 seconds to find..................and if THEY especially the EPA can't find a link how can you?

You really do need to take your, blinkers off and get real. Stating LIES as facts just shows you up as misinformed and muddle-headed.

And just so you know, petrols also produce uncombusted hydrocarbons not only diesels, so don't try that form of smearing to try and make your weak and unsubstantiated case stick either.

Diesels pollute, but petrols pollute more simply because they produce much more exhaust volume from a more polluting fuel.

I think you should go away and do some up to date "sampling and studying" before sharing your "knowledge" with the world.
« Last Edit: 17/02/2007 16:52:00 by scanner »
 

Offline snipez999

  • First timers
  • *
  • Posts: 1
    • View Profile
Hi there.
I own a diesel car, but was a petrolhead by habit for over 20 years.
I'm no techy, by any means, but if my car can do twice the mpg of my old petrol car; go twice as long between services; need less replacement parts; reach peak torque in half the engine revs and be safer for everyone concerned in the (God forbid) case of a serious accident (by carrying less easily combustible fuel) then isn't that a good thing?
 
 
 

another_someone

  • Guest
I think one question one has to ask is which NOX?

Nitrous oxide (technically not an NOX because it is N2O) has long been used in medicine, and I have not heard of it being linked as a carcinogen.

In theory, I suppose any gaseous oxide, being an acid, can cause all sorts of cellular damage, and dissolved NO2 would be one of the more potent acids.

NO is a normal part of our metabolism, although that simply means that in the right doses it will not be significantly harmful, but equally many things that are a natural part of our metabolism, if absorbed in excess, can indeed be harmful.

So, I think one should maybe be more careful than simply to lump all NOXs together (excepting that they are all potent acids, just as SOXs or even, to a lesser extent, COXs are).

As for accusing people of lying, I do not think that is in order at all.  We all have our own sources of knowledge, and whether in one case you are in error, or another case Alberto is in error - it is a very different matter to suggest that the error was by malicious intent (which is what the word 'LIES' implies).
« Last Edit: 17/02/2007 21:39:16 by another_someone »
 

Offline ROCKETRON

  • First timers
  • *
  • Posts: 2
    • View Profile
Lightarrow i have never heard of NO2 being "extremely toxic and carcinogenic" and certainly not on the same scale as CO as suggested in your post. Scanners quote from Google sounds about right to me. As i said in my previous post i am surprised that the BBC is linking to this site about a debate between petrol and diesel when people are just quoting from normal press bias against diesels and quoting theories as fact.
 

another_someone

  • Guest
NO2 may not be listed as a carcinogen, but it does seem consistently listed as a major component in photochemical smog, which certainly does have a range of health issues associated with it, even if it may be debateable if cancer is high on that list.
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
Sorry if it isn't true it's a lie, but just to placate anybody who thinks that is too strong I'll settle for terminological inexactitude and for my taste too many terminological inexactitudes are spread in the (unfathomable to me) crusade some supposedly knowledgeable people seem to have against diesel.
They seem happy to completely misrepresent and exaggerate every perceived fault of diesel but conveniently ignore all the (too my mind) far more serious faults of petrol - Volatility, flammability, toxicity, benzene http://www.epa.gov/ttn/atw/hlthef/benzene.html [nofollow] or MTBE http://www.epa.gov/oms/consumer/fuels/mtbe/mtbe.htm [nofollow] (both total environmental disasters) wastefulness and last but not least excessive CO2 emissions.

Whatever the oil industry try to do the "improve" petrol's green credentials just seem to make it ever worse for the environment.

Diesel is a safer, more economical fuel that releases less overall in the way of harmful emissions.
Cars powered by diesel are less tiring to drive due to the more relaxed way they provide motive power. They are far easier to drive in an economical manner and far more likely to actually return the MPG figure claimed for them, unlike the petrol-hybrid white elephants
http://www.consumeraffairs.com/news04/2005/hybridwatch02.html [nofollow]

So far as I'm concerned diesel in the form of bio-diesel is the only fuel that offers any large scale  long term hope for the internal combustion engine.

Whether or not that is a good thing is another argument......................

 
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
NO2 may not be listed as a carcinogen, but it does seem consistently listed as a major component in photochemical smog, which certainly does have a range of health issues associated with it, even if it may be debateable if cancer is high on that list.
If NOX from diesel is the cause of photochemical smog why is the most vehemently anti-diesel city on earth Los Angeles (where is is virtually impossible to own a diesel car) so afflicted with photochemical smog?
 

another_someone

  • Guest
If NOX from diesel is the cause of photochemical smog why is the most vehemently anti-diesel city on earth Los Angeles (where is is virtually impossible to own a diesel car) so afflicted with photochemical smog?

I did not use the words "from diesel", only that NO2 (whatever its source) is considered a major component of photochemical smog.

One reason why Los Angelas is one of the cities (there are a few others) that is particularly badly effected by photochemical smog is because the mountains around the city do not allow proper dispersal of the pollutants, so they get seriously concentrated into the valley in which Los Angeles sits.  If Los Angeles were situated elsewhere, with a different geography, the same levels of pollution pumped into the atmosphere would be more widely dispersed, and cause fewer local problems.
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
You may not have done, but others on here seem convinced that diesel produces most if not all the NOX in the world - possibly even whilst smoking a cigarette or two, sat in front of an open (or gas) fire or in a house heated by gas or electricity.
 

another_someone

  • Guest
You may not have done, but others on here seem convinced that diesel produces most if not all the NOX in the world - possibly even whilst smoking a cigarette or two, sat in front of an open (or gas) fire or in a house heated by gas or electricity.

From what I read, it seems that NO2 in photochemical smog is caused substantially by NO2 and O3 production caused by an interaction of NO, unburnt hydrocarbons, and sunlight.  Most of the NO2 does not seem to be directly coming from the exhaust of vehicles, but as a secondary product created in the atmosphere.

Thus, pumping out high levels of NO alone will not do it, it requires both the NO and the hydrocarbons.

As has been indicated here, the vehicles that produce a lot of one, tend to produce less of the other.  Thus one might argue the worst case scenario is for a mix of vehicles each adding their own contribution.  Where that leaves us with regard to which type of vehicle is more to blame for the outcome is a more difficult question.
« Last Edit: 17/02/2007 22:56:50 by another_someone »
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
Well I trust Alberto will believe you..........

 

another_someone

  • Guest
Well I trust Alberto will believe you..........

I am not some supreme being that expects unquestioning belief, and should you or Alberto choose not to believe me (for whatever reason), I should not be mortally offended, nor accuse you or he of heresy or blasphemy.  The only thing I do ask is the you trust that I am telling the truth as I know it (and being human, I am as susceptible to error as anybody else).  I just ask that nobody assume malice or deliberate lies, even if maybe they cannot find cause to agree with me.
 

Offline scanner

  • Jr. Member
  • **
  • Posts: 26
    • View Profile
Fair enough no one could ask more than that.

If Alberto wants something to worry about this substance http://www.dhmo.org/ [nofollow] kills far more people every day than any exposure to NOX from whatever source.

It destroys landscape, infrastructure and technology with equal ease.

All in all it is deadly stuff and we are considering replacing IC engines with motive sources that are said to produce this as their only emission.

Are we mad?
 

another_someone

  • Guest
If Alberto wants something to worry about this substance http://www.dhmo.org/ kills far more people every day than any exposure to NOX from whatever source.

It destroys landscape, infrastructure and technology with equal ease.

All in all it is deadly stuff and we are considering replacing IC engines with motive sources that are said to produce this as their only emission.

Are we mad?

LOL - I first heard about that some many, many years ago - but I do think it still holds a valuable lesson in human gullability.
 

Offline Hadrian

  • Neilep Level Member
  • ******
  • Posts: 2175
  • Scallywag
    • View Profile
Quote

I am not some supreme being that expects unquestioning belief, and should you or Alberto choose not to believe me (for whatever reason), I should not be mortally offended, nor accuse you or he of heresy or blasphemy.  The only thing I do ask is the you trust that I am telling the truth as I know it (and being human, I am as susceptible to error as anybody else).  I just ask that nobody assume malice or deliberate lies, even if maybe they cannot find cause to agree with me.




i can say that you are one great chap who i have enjoyed a scrap or two with in the past and you never took prisioners on the way and i vary much respect you for it...


 

Offline neilep

  • Withdrawnmist
  • Naked Science Forum GOD!
  • *******
  • Posts: 20602
  • Thanked: 8 times
    • View Profile
Can I just say that me is well happy for asking my question.

Everyone is being so nice and lovely !!!..

Big Big soppy hugs all round.

YAYYYYYYYYYY !!!!






*if you detect even a soupcon of sarcasm...then ewe may be right*
 

The Naked Scientists Forum


 

SMF 2.0.10 | SMF © 2015, Simple Machines
SMFAds for Free Forums