Buying advice!

Discussion in 'General Discussion' started by ajs37, Aug 4, 2008.

  1. kth286

    kth286 MB Enthusiast

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    Because what started out as a very simple concept years ago has now become very very complicated compared to the normal non turbo petrol engine.
    I have been watching the steadily increasing problems on the forum with diesel engined cars and the costs often quoted for fixing them is very high.
     
  2. hawk20

    hawk20 MB Enthusiast

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    Maybe you've failed to notice how complex the petrol engines have become and how much some of them cost to fix. Pretty even Steven on the complexity front IMO.
     
  3. kth286

    kth286 MB Enthusiast

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    Most petrol engined cars do not need a turbo, but a diesel car needs the turbo and all the complication that involves to get any effective performance.
     
  4. hawk20

    hawk20 MB Enthusiast

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    First MB have said all their cars will have turbos by 2010
    Second diesels don't need all the Electronic fuel injection and electric spark pluggery that modern petrols do.
     
  5. grober

    grober MB Master

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    I think I am with KTH286 on this one. Electronically controlled/ common rail / direct injection / variable nozzle turbo diesels are indeed pretty complex bits of kit. There are many documented examples of turbo seals/bearing failure, very expensive high pressure pump failure, premature glow plug and direct injector failure with concomitant removal/renewal from cylinder head problems. And lets not forget the good old EGR valve which seems to only last 20-30k miles in any turbo'ed engine. Add on the need to use special low ash oils to maintain particulate filter integrity and the increasing fuel duty on derv and the argument for ownership of a modern diesel engined mercedes benz with high mileage or out of warranty may not so strong in comparison with the old indirect mechanical injection diesel engined cars.

    Comfort of a sort is at hand though for high mileage diesel owners since it would appear that more complex petrol engines are also finding their way on to the second hand market . Highly tuned direct fuel injection, turbocharged or supercharged( kompressor) small capacity petrol engines would appear to be the powerplants of the future and I would assume these will share all the diesel problems detailed above. I would hate to be the tech tasked to sort out the new VW supercharged/turbo charged engine for example when it goes wrong ---as undoubtedly it will. http://car-reviews.automobile.com/n...upercharged-engine-for-mass-consumption/1414/


    In summary at this particular moment in time if I was buying a high mileage out of warranty Mercedes Benz I reckon a normally aspirated petrol engined car is the best way to avoid potentially expensive repairs/component replacement---- all other things being equal.
     
    Last edited: Aug 11, 2008
  6. hawk20

    hawk20 MB Enthusiast

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    Grober: most current MBs don't have particulate filters (they meet EU4 without) and don't need low ash oil. Mine takes simple Mobil 1

    Odd that most professionals choose diesel for high mileage.
     
  7. verytalldave

    verytalldave MB Enthusiast

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    Both diesel and petrol have their strengths and weaknesses. It depends what you personally want from your car. This will point you more towards one fuel more than the other.
    Diesel gives you much better fuel consumption and low down torque. This suits commercial vehicles and cars subject to higher mileage use.
    Petrol is quieter and gives a wider power band. Generally higher fuel consumption, but this is offset by lower fuel prices and longer periods between service intervals. Many other points to consider of course, but its all down to individual requirements.
     
  8. hawk20

    hawk20 MB Enthusiast

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    Here we go again. The digs at diesel. Why cannot petrol engine lovers just love their engines without knocking others.

    And your view is so out of date. Diesels do not have shorter servicing intervals any more. Long gone. My S did 18k between services on ASSYST. My brother's A class does well over 15k between services.

    'Petrol is quieter' you say but that is really only at tickover (and even then not true of the latest MB diesels). Go and try the new S320cdi. It is amazing.

    My A class does 40 miles per thousand revs becuase the diesel has so much torque. At 80 the engine is purring at only 2k revs - way less than a petrol- and very quiet indeed.

    Have a look at road tests which scientifically compare petrol and diesel cars noise levels at 70 mph etc. Nothing in it.

    And the better fuel consumption is NOT offset by higher fuel cost. The two litre diesel A class (called the A180cdi) does 37% more miles per gallon than the two litre petrol A class. Yet diesel costs only 10% more. It pays, whether doing low or high mileage. And the residuals are higher too. Great engines. Love 'em.
     
    Last edited: Aug 11, 2008
  9. verytalldave

    verytalldave MB Enthusiast

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    Best advice........

    Drive both and see which YOU prefer.

    Hawk20 prefers diesel. I prefer petrol.
     
  10. hawk20

    hawk20 MB Enthusiast

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    Peace and harmony. On that we agree.

    By the way I love petrol engines too -genuinely. I had an E280 straight six around 1990 and that was one beautiful engine. Autocar said it was 'the best engine of any size, in any car, of any make, anywhere in the world, at any price.' Fabulous.

    But please do try the new V6 320cdi from MB. I tried it in the S class but I assume it is the same in the E and ML etc. Stand outside on tickover and you would swear it was a petrol engine. Even open the bonnet and stand outside on tickover and you would swear it is a petrol engine. So quiet, so smooth. Really an amazing engine.

    But the old straight 6 320cdi was a cracker too. Noisier yes, but still great. Straight sixes are more economical other things being equal and the kick in the back when you put your boot down was just lovely. Great lumps of torque (as much as the 5 litre V8 petrol IIRC). Much more of a kick in the back than on the new super smooth V6 one. Both great though.

    If it weren't for the govt and the widespread attack on gas guzzlers from all quarters I would choose either a 5 litre V8 petrol or try the new 4.2 litre diesel on the ML and GL. Awesome.
     
  11. verytalldave

    verytalldave MB Enthusiast

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    My experience of comparing diesel and petrol comes exclusively from when I bought my C Class W203 just over a year ago.
    Knowing the basic differences between the two, I test drove both a 2004 C200K and a similar diesel engined W203 (I dont know which engine this car had). The differences I noted was that the power delivery of the diesel was like a train, but ran out of puff above 3000rpm - or thereabouts. However this was fast. Petrol was quieter. Power was not all that much low down, in fact almost slow. However, as the revs picked up, it began to really move.
    So that was it. Both had their points, but for me, it was the sound of the petrol that sealed it.
    And only doing about 10K miles a year, cost was never a consideration.

    BTW, I read somewhere, some time ago that a straight 6 engine was perfectly balanced. Better than a V8, V12, or any other combination. Dont quite see the logic, but I accepted it on face value. I had an old Triumph 2000 estate of 1974 vintage and its engine certainly was smooth and unfussed. Performance was the same empty or fully laden - almost.
     
    Last edited: Aug 11, 2008
  12. hawk20

    hawk20 MB Enthusiast

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    Correct. Imagine the 6 cylinders in a straight line. One and Six -perfectly balanced forces on the crankshaft. Two and five -ditto. Three and four -ditto.
     
  13. st4

    st4 Banned

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    Thats why IMO its the best type of engine to have in a car.
     
  14. hawk20

    hawk20 MB Enthusiast

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    My instinct too. But try the new 320cdi. It is amazing.
     
  15. st4

    st4 Banned

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    I won't want to as I'll become discontented with my 220cdi, and I'll just hanker after the E280/320cdi all the more as I know I'll love it.

    (I'm not on a PCP though so when things improve....:D:rock:)
     
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