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  1. #1
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    Default Diesel vs. Petrol Energy Considerations

    I see a lot of diesel vs petrol discussions on the forum and have myself faced a choice diesel or petrol vehicle. i am not going to get into the fun and games of the argument but will mention something interesting.

    At the pump we buy fuel per litre. Prices are also per litre. A much respected professor has once mentioned in one our discussions, have you ever considered the energy side of diesel to petrol argument? Hmmm, I said. The jist of it is:

    Density

    Diesel density: 870g/l or 870g/dm^3
    Petrol density: 740g/l or 740d/dm^3

    resulting in

    Energy value:
    Diesel: 38.6MJ/l
    Petrol: 32.0MJ/l

    Thus a 100l tank of diesel has 17.5% more energy i.e. 10l/100km petrol consumption is much the same as 8.25l/100km for diesel.

    Suggestions have been made in Europe that fuel should be sold according to energy content, the diesel savings become shaky. Another cool thing is the cyclic repitability of diesel which gives it improved torque qualitites and efficiency. I have videos about it but thats another topic

  2. #2
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    Default

    To me there are THREE considerations:

    1) Purchase price of the vehicle. On most brands the diesels are just TOO expensive when compared to the petrol equivalents.

    2) Fuel economy. On cars the fuel saving hardly, if ever off sets the initial extra costs. On bigger vihicles and 4x4's the savings are much more drastic and another look is waranted ....

    3) "Clean diesel". most waranties now insist on clean diesel. Yet it is not that easy to get clean diesel (ie low sulpher diesel). This HAS improved in the last year, and will hopefully be sorted in the next few years.

    4) Reliability - it seems the secret to long diesel life lies in an EGT meter. Pity these are not standard items, YET.

    5) with the stuff we get upto diesel has advantages when it gets to water crossings ...



    Uhm, seems there are more than three things to consider ....


    I AM following these threads closely - a diesel may just be in my future ...... after all I learnt to drive in a diesel ISUZU, the original 1900cc non turbo.

  3. #3
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    Default only one thing

    Hi,

    Only two things to concider.

    Drive a 1.9 TDI POLO Sportline. 97Kw and 400Nm and open road consumption of less than 5L/Km and blow nearly every hot hatch away at the robots, and especially on the hills.

    Also try my other car, RRS TDV8 , 200Kw + and 650Nm and nearly three tonnes, and Durban Joburg at less than 10Km/L at highway speeds. And skrik vir niks at the robots.

    Its a diesel thing.

    Have a look at the best Turbo Diesel motor on the market, Toyota 3.0 D4D, in every way it is better than the petrol versions, Hiliux and Fotrtuner and Prado. (I cant believe I actually said something good about a ATOYOT)

    Just my views.

    Cheers
    Fluffy

  4. #4
    4ePajero Guest

    Default

    Quote Originally Posted by Fluffy View Post
    Have a look at the best Turbo Diesel motor on the market, Toyota 3.0 D4D,.....

    ..... Just my views.
    Good engine, for sure!
    Best?
    There are similarly good engines!


  5. #5
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    Default

    I am quite undecided on the issue as i have enjoyed both engines a lot. Mechanically i can say, diesels are more high tolerence machines, no two ways about it. Older ones will deal with some mistreatment but not the new ones.

    I have just returned from diner with a friend who's family is in Luanda and 50ppm diesel there is, i quote: "Ask at the pump if they have 50ppm and they look at you like you are on something" Yet they have no injector issues etc.

    As far as sedan performance, i have a kompressor mercedes that gives me 7.5l/100km at way past legal speeds, so now reason for me to own a diesel past warranty. Pumps and injectors in due time, cost plenty. so can the kompressor...

    When it comes to SUVs, well i just got a petrol cause Fortuners have no auto D4-D 4x4 and wife would have none of that.

    As far as robot to robot, i am firmly against that for diesel. New, under warranty, yeh give it foot. Pick up tabs past warranty and maintenace, hmmm.

    Recently my colleagues carried out a test programme on 4 Euro 4 high performance diesels, using fuels and lubricants not yet available in SA. The test was extremely harsh, much like robot to robot acceleration and idling and not letting the engines warm up etc, resembling full engine life in 1000hrs. The result was R550000 parts in 4000hrs running (1000hrs per engine). Turbos, heads, pistons in half and more. So for me, in IMHO only, a diesel is for use as many on this forum do. Overlanding, reasonable speeds and acceleration. Thorough observation of warm up and cool down. Servicing. Then a diesel will serve you. Chase hot hatches and it will show teeth soon enough

    Fluffy: Is the polo chip tuned? They have 310Nm standard.
    Last edited by Sergey; 2009/11/21 at 11:26 PM.

  6. #6
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    Default Yes.

    Fluffy: Is the polo chip tuned? They have 310Nm standard.


    You are absolutely right.

  7. #7
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    Default

    Fluffy: Thats one evil polo Add difflock and one could overland in it.

  8. #8
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    Default

    Quote Originally Posted by Fluffy View Post
    Hi,

    Its a diesel thing.

    Have a look at the best Turbo Diesel motor on the market, Toyota 3.0 D4D, in every way it is better than the petrol versions, Hiliux and Fotrtuner and Prado. (I cant believe I actually said something good about a ATOYOT)

    Just my views.

    Cheers
    Fluffy
    .
    The 3.0L D4-d in the Land Cruisers is the benchmark for many engine manufactures.
    Economy and power, this D4-d wins hands down every time.
    .
    Liters per km
    0,09



    Liters per 10 km
    0,94



    Liters per 100 km
    9,42



    Kilometer per liter
    10,62

    at a steady 95 km/h towing. and loaded. and good economy.
    .

    .
    ok, I wasn't driving fast, just a steady, 'get me home economical' speed, but when I have just me and the other half, the LC will run up past 170km/h without any difficulty, but watch the fuel gauge drop. .

    Then there is the 'Toyota Motorsports' diesel chip upgrade, bringing engine power up to 150 kW. (200 + HP )
    .
    http://www.tte.de/popup/TTE/cm_landc...ormancekit.htm
    .


    Now the fun begins,


    'vette
    Last edited by uk_vette; 2009/11/22 at 05:25 PM.

  9. #9
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    Default No Robo's

    Hi Sergey,

    When I say that they can do robo blasting and all the other things, all I meen is that they can, not that we actually do. Mind you dont know what the ankle biters do when the borrow the cars.

    SWAMBO's quest is to achieve below 5L/100Kms on a regular basis so the Polo is less stressed than a coconut on a deserted island. When VW did the recent Turbo recall the technician told us that her Polo Sportline TDi is the best preserved one in KZN. (Ultra low mileage and no hard work)

    South Africa's high altitude (Gauteng), high temperature summers and long high speed open freeways are a recipe for disaster for a Turbo diesel if you dont know what you are doing. Cruising at 140Km/h for hours on end with a load, will eventually kill it.

    EGT gauges are great, but an oil temp gauge is also usefull (ala VW Touareg) Push the car hard ,especially towing a big deep sea ski boat, when the oil temp rises, back off.

    Cheers
    Fluffy

  10. #10
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    Default

    Hi Fluffy,

    I am of the same opinion on cruising. My folks live up in North Nam, and for them to go anywhere near civilisation, its no less than 500km in 45 degree heat. Our diesel hated it. Friend's one too. Plus there is always the matter of wanting to get there a bit quicker as you only have a weekend to go shopping and see friends. We still have the diesel pajero, after i rebuit it, i IMPOSED 120km/h family speed limit on it and it has been purring happy for 5 years now. We fish and cruise around the North gravel routes to Skeleton Coast with it. I love the calming diesel purr on a gravel road in the middle of nowhere. For everything else there is a 4.0L V6 and no cries about consumption.

    My dad's very close friend is a "boer" through and through, quite funny actually, as they don't speak each other's language yet get along super!!! Stephen speaks Afrikaans, dad speaks English...and brandy translates Stephen has a FLEET of vehicles, i don't even know how many. They were all diesels and used for his construction works all over the north. Stephen does not know driving styles other than "as fast as i can get there". Nowdays he drives petrol for these reasons.

    Therefore i always say, buy a diesel, take care of it and it will take care of you!!! Take it for granted, it will take half your wallet. Much like a woman i should say

    Regards
    Sergey

    P.S.
    ROFL, in Russia we call them "back gnawers" When i was 17, i took my dad's Sentra and ruined two CVs in one night by doing impressions of Sebastien Loeb in the bush on the Angolan border near Rundu Had to make lots of "seemingly clever" excuses later
    Last edited by Sergey; 2009/11/22 at 06:59 PM. Reason: P.S.

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