Top Gear economy challenge

Discussion in 'General Discussion' started by V12, Dec 11, 2008.

  1. V12

    V12 MB Club Veteran

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    After watching the recent economy challenge where the jag won the race to do 750 miles on one tank, it got me wondering if it were at all possible in a Merc! The most i remember reaching was 600miles on a round trip to scotland in my e320cdi.

    As my car has just been written off and i have been borrowing cars from friends and family i set about finding the car for the job.
    Right under my nose, my dad had just picked up a dirt cheap 2000 E220cdi classic with a 6 speed manual - perfect for the job, having the same size diesel tank as the e320cdi.

    The car in question is a pretty standard model with 205/65/15 tyres on steel wheels, has 125,000 on the clock and runs purrrfectly. Oh and it's black, which definately helps the testing!

    On my first day of testing i reached a brilliant 61mpg.

    Second day 62.9 mpg

    third day 66.9 mpg

    I stupidly started "practising" my economy driving skills without filling the tank, so i'll have to fill up tomorrow and start the test again. Although not quite as fair as their test where they could pretty much just drive all day long, i'm just driving over 30miles to work and then back again every day, but we'll see if it can be acheived and if the On Board Computer is accurate at all.

    The On Board computer reports 14.2 gallons once filled to the brim, while mercedes quote it as having a 17.6 gallon tank.

    If the on board computer is correct and it really is returning 66.9mpg that means a tank could theoretically return 1177.44miles.
    That of course, is an outrageous figure, that i'll never achieve, but it will be interesting to see how close i get.

    My driving tactics are as follows. Cruise control on at 56mph, so as to never slow down slower than a truck, speed upto 70 on the long down hills (coasting where possible) to make the engine work less on the up hills as i nurse it back down to the 56mph on the up hills.

    OK, this is all a little extreme, but i like a little experiment from time to time. And seeing as a lot of traffic seems to travel at these speeds anyway these days, i'll take a few weeks off from the outside lane for the benefit of this test.

    Any comments/input welcome.
     

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  2. Dieselman

    Dieselman Banned

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    Is the tank defiantely the same size as a 320 Cdi tank.?
    If the computer thinks there is only 14.7 gallons instead of 16 gallons it will be over-reading by 20% or so.

    If you are really serious about obtaining better economy fit an EGT gauge as you can see the load on the engine increasing immediately so remain more focussed.
     
  3. A210AMG

    A210AMG MB Club Veteran

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    Should easily be possible.

    When the fuel strike was on my dad managed over 50mpg from his 2003 E320cdi Estate.

    Reading the road, coasting and a light foot should see some good figures.

    Dads gave a range of well over 1000 miles when he was getting 50mpg. I don't think that actually works out though but even normal driving he has a huge amount out of it. Generally on a good run to Annecy using the tolls.

    Don't forget on top gear they also sealed the seems on some of the joints with gaffer tape and even drove with the mirrors folded in :) a little extreme..


    Good luck.
     
  4. gbjeppm

    gbjeppm Hardcore MB Enthusiast

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    Last edited: Dec 11, 2008
  5. OP
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    V12

    V12 MB Club Veteran

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    From what i read it definitely has an 80litre tank in it the same as my e320cdi.
    80 L = 17.5975 gal(UK). Is that correct?

    I don't know how low the fuel sender unit goes in the tank personally, it may be that the reading for the OBC is way out as it doesn't reach the bottom, but you are right, that's a huge difference.

    Best way to find out, is to run this thing dry and then fill her to the top i guess!

    I don't want to stop my life for this test and certainly don't want to shell out for any fancy equipment, just pure old fashioned driving talent! ;) :p

    Unfortunately this classic doesn't have folding mirrors, the electric windows don't even work in the back, it's a bit of a shed but drives lovely and goes really well.
     
    Last edited: Dec 11, 2008
  6. gbjeppm

    gbjeppm Hardcore MB Enthusiast

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    Thats correct:) :rock:

    Well there goes my theory!!
     
  7. pauldmaynard

    pauldmaynard Active Member

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    320 CDI has an 80l tank but the 220 cdi has a 65l tank
     
  8. Mactech

    Mactech Hardcore MB Enthusiast

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    Those are some really good mpg figures!:)
    You will have to check that the meter is telling the truth, but you seem to have got the right idea to a saving fuel!
    I wonder if this new method of driving has made any real difference to your journey times?
    In my own experiments I have found that traffic conditions really dictate your journey time and if you are arriving late, then you should have started earlier!;)
     
  9. OP
    OP
    V12

    V12 MB Club Veteran

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    Makes more sense. 65 L = 14.2980 gal

    That means both my e320cdi and e220cdi have this size tank though, as they definitely take the same amount of diesel to fill up.
     
  10. OP
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    V12

    V12 MB Club Veteran

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    Just confirmed...80l tank was a £70 option when new...
     
  11. Dieselman

    Dieselman Banned

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    IIRC the standard tank on a w210 is 70L the upgraded tank is 80L.

    All petrol models other than n/a 200 have the larger tank and all diesels other than 320 Cdi have the smaller tank.

    A VIN check will reveal whether the upgrade is fitted.
     
  12. jimti

    jimti Hardcore MB Enthusiast

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    I wonder why you pick a figure of 56 mph is it the most economical for the car? I would doubt it, the only reason it is used in car mpg figures is AFAIK it is 90KPH (the speed limit on most European single carriageway roads roads) so is a figure most drivers want to know. I don't know much about fuel efficiency, but would think 45 to 50 mph would give you far better fuel returns, the exception is if you can slip stream a truck, that may help as wind resistance will be the biggest drag factor when you drive
     
  13. Dieselman

    Dieselman Banned

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    I tried this last night on the motorway and couldn't see any difference on my EGT gauge, which would indicate that it makes no difference in reality.
     
  14. W210 Fan

    W210 Fan Hardcore MB Enthusiast

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    but doing 30 miles to work and back will not give you the same range the top gear lot got as they were not doing stop start journeys but one long stint on the motorway which is a more efficient way of travelling fuel wise, btw I also think that 56mph may be a great way to achieve a great figure as you can sit behind the trucks at the speed in their aerodynamic wake getting sucked along and get a slightly false but very high figure,
     
  15. OP
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    V12

    V12 MB Club Veteran

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    Anything lower than 55mph does strain the engine in 6th gear and i lose economy slightly.
    Biggest reason for this speed is that after all i am travelling on dual carraigeways and for some part, the motorway, and i refuse to travel slower than the trucks...that's just ridiculous and un-safe in my opinion.
    It has only seemed to have added a couple of minutes to my journey time compared to when i set my cruise at 70mph for the whole way.

    Thanks for the input W210 Fan.

    As previously stated "Although not quite as fair as their test where they could pretty much just drive all day long, i'm just driving over 30miles to work and then back again every day, but we'll see if it can be acheived and if the On Board Computer is accurate at all."

    As far as drag and slipstream go, anyone that rides a motorbike will tell you about this...
    I have a Suzuki Bandit and also ride my dads Blackbird quite a bit, to feel any clean slipstream from a large vehicle you have to be so close that you are practically touching it. If you sit at a comfortable distance the "choppy" air from the un-aerodynamic trucks actually makes it really hard work on a bike.

    Yes i know the bike is completely different from a car, but the same principles apply and i find only sitting very closely behind a sports car i can get somewhat of a smooth airflow from them.
     
  16. OP
    OP
    V12

    V12 MB Club Veteran

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    Parkers has both the E220 and E320 down as a 65l tank as standard, can't seem to find many other sources to back this up or disprove it though.
     
  17. jimti

    jimti Hardcore MB Enthusiast

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    You don't need to know the size of your tank for the test, just start at full, run it until it reads nearly empty, fill it again and work out the MPG, then you can work out the possible mileage from either size tank.. I bet the figures will be good though looking at what you are achieving already
     
  18. OP
    OP
    V12

    V12 MB Club Veteran

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    I'll be running the tank till the car cuts out and then refilling with a 5l can and then driving to the nearest station immediately.

    The point is indeed to simply see how many miles are possible from the tank, but it would be nice to know before hand if i have a 65l, 70l or 80l just for theories sake.

    I guess i'm just being too **** about it then...
     
  19. Dieselman

    Dieselman Banned

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    Estates should have a 65 litre tank, saloons 70Litre, larger engined saloons 80 Litre.
    Check the VIN in the Rusky VIN checker to see whether yours has a larger tank option fitted. Mine does.
     
  20. Peter DLM

    Peter DLM Hardcore MB Enthusiast

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    I believe the BlueMotion Polo 'won' the economy challenge.

    The jag just had an enormous tank and dodgy fuel level sender/fuel computer. Oh, 53mpg isn't too shoddy either.

    I ran my E320 as low as I dare on unleaded the other day, the computer showing 0.0 litres, and o miles left for a couple of miles and I recall sticking in around 65 litres to brim it. I have no idea if the fuel level sender was lying or not.
     

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