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What is the difference between a petrol and a diesel engine

geek84
geek84 Posts: 1,126 Forumite
Part of the Furniture 500 Posts Combo Breaker
Hi Folks


I am in the process of buying a new car, and still deciding whether I should go for a petrol or a diesel engine. Can someone please explain the difference?


I will only be using the car on short distances and only be driving long distances - going on the motor way about half a dozen times in the year.


Thanks in advance for you responses.
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Comments

  • facade
    facade Posts: 7,383 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    If it is a brand new car, you need a petrol engine.
    New diesel engines have something called a DPF (diesel particulate filter) to catch the soot. It quickly fills up with soot, and when the car is doing about 70 mph for about 30 minutes it "regenerates"( basically sets this carbon on fire)
    They give no end of eye wateringly expensive trouble when used mainly on short trips.

    (Naturally, the DPF is a "wear & tear" item that is not covered under warranty.)
    I want to go back to The Olden Days, when every single thing that I can think of was better.....

    (except air quality and Medical Science ;))
  • geek84
    geek84 Posts: 1,126 Forumite
    Part of the Furniture 500 Posts Combo Breaker
    Thanks for your reply, facade.

    What do you mean buy They give no end of trouble when used mainly on short trips.
  • 4743hudsonj
    4743hudsonj Posts: 3,298 Forumite
    edited 7 June 2014 pm30 1:04PM
    As above avoid Diesels but id take issue with the word "new". Cars as far back as the 80's have them fitted. Citroens at least have had them as standard since the early 00's.

    Even if the dpf wasn't a factor, id still say petrol merely due to the cost of maintenance being generally lower for petrols. On short journeys the fuel savings of a diesel will not be enough to outweigh the higher purchase and maintenance costs.

    The DPF is essentially a filter. Diesels create soot which usually goes straight out into the air. If you have ever seen a car putting out black smoke you will know what i mean. This is now captured by the dpf. When this gets hot enough, the ash inside is burnt to much cleaner particles. If you only do short journeys, the filter never gets hot enough and you end up with a filter completely clogged with ash.

    In my Skoda, the ash required before replacement is needed is just 46 grams!

    A clogged filter will essentially cause the cars ecu to limit power and if not resolved, you WILL require a new/cleaned filter. These range in costs from £1000-3000.

    Get a petrol.
    Back by no demand whatsoever.
  • facade
    facade Posts: 7,383 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    geek84 wrote: »
    Thanks for your reply, facade.

    What do you mean buy They give no end of trouble when used mainly on short trips.


    They block up completely with soot, then a light comes on telling you to go to the dealer immediately, and the engine goes into limp home mode.

    When it goes to the dealer, you give them a wheel barrow full of money, and they plug their electronic gizmo in, simply press a button (must take all of 30 seconds to do), and the car runs at maximum rpm for half an hour (they have to stand them on concrete, as it will melt the tarmac under the car ;)) this gets the dpf hot enough to burn out all the carbon.

    then it is ok again for a few weeks of short trips.

    Sometimes they sell you a new dpf, then you will definitely need a large wheelbarrow for the cash ;)
    I want to go back to The Olden Days, when every single thing that I can think of was better.....

    (except air quality and Medical Science ;))
  • facade
    facade Posts: 7,383 Forumite
    Part of the Furniture 1,000 Posts Name Dropper
    As above avoid Diesels but id take issue with the word "new". Cars as far back as the 80's have them fitted. Citroens at least have had them as standard since the early 00's.

    .

    Agreed, but at least brand new means there must be a dpf.

    The last diesel I had was a cavalier, with the isuzu engine. Brilliant engine, only needed oilchanges, filters, cambelts and the valve shims grinding down once to get it to over 200,000 miles.

    Probably difficult to find a good one now, but you never know......
    I want to go back to The Olden Days, when every single thing that I can think of was better.....

    (except air quality and Medical Science ;))
  • force_ten
    force_ten Posts: 1,931 Forumite
    Eighth Anniversary 1,000 Posts Combo Breaker
    the choice between petrol and diesel should be made on driving style and the type of motoring that you do

    if the car is to be used for the school run, trips to the supermarkets , or to pootle around town then your only realistic choice is petrol or petrol hybrid

    if your driving is made up of long high speed motorway runs on a regular basis and then your normal shopping trips and the like then a modern diesel may be ok for you

    I currently drive a 2.0L diesel that has a DPF (diesel particle filter) and do about 10,000 miles per year, my car is not used to and from work or for short trips around town when my car is used a short trip will be about 36 miles round trip often 200 miles plus in a day giving the DPF plenty of time to regenerate

    if you use a modern diesel to pootle around town then you will block the DPF and the car will go into limp home mode, if the DPF becomes completely blocked then it will need replacing, on my car the DPF is £1700 for an exchange unit plus fitting so it is a two grand job
  • force_ten
    force_ten Posts: 1,931 Forumite
    Eighth Anniversary 1,000 Posts Combo Breaker
    geek84 wrote: »
    Hi Folks


    I am in the process of buying a new car, and still deciding whether I should go for a petrol or a diesel engine. Can someone please explain the difference?


    I will only be using the car on short distances and only be driving long distances - going on the motor way about half a dozen times in the year.


    Thanks in advance for you responses.

    Buy a Petrol don't buy a diesel, for the type of driving that you list then petrol is the way to go
  • Strider590
    Strider590 Posts: 11,874 Forumite
    As above, for that sort of driving a diesel will be a money pit.
    “I may not agree with you, but I will defend to the death your right to make an a** of yourself.”

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  • DUTR
    DUTR Posts: 12,958 Forumite
    Part of the Furniture 10,000 Posts Name Dropper
    geek84 wrote: »
    Thanks for your reply, facade.

    What do you mean buy They give no end of trouble when used mainly on short trips.

    They mean that you are seeing what you want to see as in claimed MPG's , in practice the driving you will do mostly do will not warrant many benefits of the soot chucker, around town in urban traffic, you are unlikely to see much of a 20% gain in MPG.
  • Messa
    Messa Posts: 66 Forumite
    It used to be said that you need to do over 15,000 miles a year in a diesel to recover the additional purchase cost and fuel price, don't know if that still applies. I have a diesel but would recommend a petrol.
    There are 10 types of people who understand binary, those that do and those that don't !
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