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Thread: Fuel economy

  1. #1
    Senior Member Tony Sirett's Avatar
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    Fuel economy

    Evening all quick question on fuel economy and cruise control, in my old 3.0L S type on a long drive if i stuck it in cruise control at 58 - 60mph i used to get 450+ miles to a tank of fuel, on my 3.0L PL diesel i don't seem to be getting anywhere near that much 390 miles is my best so far.

    Any one else give me some ideas on best cruise speed and how many miles i should be getting for a tank?

    Thanks Tony
    2009 09 plate 3.0 Diesel PL XF
    2004, 54 plate Ford Ranger 2.5 diesel custom paint work.
    1963, Ford Consul Classic 2 door under restoration.
    2016, Triumph America 865.
    2003, Yamaha V Star 1100 Classic.

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    Senior Member Jimbov8's Avatar
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    You may have a slightly smaller tank on the XF Tony, which will also have an effect.
    Jim.
    2012 XKR Black pack, Speed Pack, Aero pack, Rat pack. Past:-87'XJS 3.6L, 93'XJ40 3.2L gold, 95'XJ6 4.0L sport, 00'XJ8 3.2L sport, 2005 XK8 4.2L coupe, 2009 XK 5.0L Portfolio in that order and enjoyed all of 'em.

    I do not offer advice, I only say what I would do with the set of circumstances presented. Your choice always.

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    I usually get around 600 miles to a tank on my 3.0d on my daily commute at fast motorway speeds. Best I have seen is 625 in the warmer weather.
    Jaguar XFS 3.0d 2017 Loire blue

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    Senior Member Robinus's Avatar
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    Have you brimmed the fuel tank & checked how much to re-brim it ? Your true mpg may also be calculated from this. I think the tanks are the same size.

    If you're going by the fuel gauge, some of them lie.

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  8. #5
    Senior Member Tony Sirett's Avatar
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    Best speed to sit at on motorway for fuel consumption?
    2009 09 plate 3.0 Diesel PL XF
    2004, 54 plate Ford Ranger 2.5 diesel custom paint work.
    1963, Ford Consul Classic 2 door under restoration.
    2016, Triumph America 865.
    2003, Yamaha V Star 1100 Classic.

  9. #6
    Senior Member Jimbov8's Avatar
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    Try 1800 revs Tony, though I don’t use cruise if I’m looking for best mpg’s.
    Jim.
    2012 XKR Black pack, Speed Pack, Aero pack, Rat pack. Past:-87'XJS 3.6L, 93'XJ40 3.2L gold, 95'XJ6 4.0L sport, 00'XJ8 3.2L sport, 2005 XK8 4.2L coupe, 2009 XK 5.0L Portfolio in that order and enjoyed all of 'em.

    I do not offer advice, I only say what I would do with the set of circumstances presented. Your choice always.

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  11. #7
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    According to studies backed by the department of energy, the average car will be at its advertised MPG at 55 mph. But as the speed increases:

    - 3% less efficient at 60 mph
    - 8% less efficient at 65 mph
    - 17% less efficient at 70 mph
    - 23% less efficient at 75 mph
    - 28% less efficient at 80 mph

    http://www.mpgforspeed.com/

    So, for most cars, the "sweet spot" on the speedometer is in the range of 40-60 mph. Cars with a higher road load will reach the sweet spot at a lower speed

    If you drive your car in the "sweet spot" you will get the best possible mileage for that car. If you go faster or slower, the mileage will get worse, but the closer you drive to the sweet spot the better mileage you will get

    https://auto.howstuffworks.com/fuel-...estion4771.htm
    XF SV8 A - USB 2 - B&W 440W - Parking Aid Pack with Rear Camera - CAT Suspension - TPMS - 20" Volans - Headlamp Powerwash - Rain Sensitive Wipers - Xenon Headlights - Heated Windscreen - Intrusion Sensing - Navigation with DRG and TIS - ACC - Forward Alert - Memory Function - Blind Spot Monitor - Bluetooth Connectivity - Automatic Headlamp Leveling - JaguarVoice

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    Senior Member Tony Sirett's Avatar
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    Drove down to Portsmouth and back, 63mph on cruise control and mpg was 41.2mpg, which if I'm being honest is rubbish, my 2002 3.0L mercedes cdi estate used to get 54.7mpg on the same journey, think my car might need looking at.
    2009 09 plate 3.0 Diesel PL XF
    2004, 54 plate Ford Ranger 2.5 diesel custom paint work.
    1963, Ford Consul Classic 2 door under restoration.
    2016, Triumph America 865.
    2003, Yamaha V Star 1100 Classic.

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    I found on my previous 61 plate 3.0d PL pre facelift that around town it was low 30's and on a run being sensible it was high 30's to low 40's depending on weather/ fuel used. Best I saw was 48 in the roadworks on M6 where it was limited to 50mph.

    I've found my current car is more economical, typically 4-6 mpg more on same use, which I put down to stop start/ 8 speed gearbox.
    XF MY15.5 3.0d S Portfolio Stratus Grey with Ivory interior.

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    Senior Member jberks's Avatar
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    On the run back home from Liverpool to Leeds (80 miles) on Thursday, queued out of Liverpool (25 mins of stop start), 10 miles of 50 but the rest ranging from clear roads at 85 to sluggish traffic. Got into Leeds and checked the mpg at 46. By the time I’d queued the remaining 8 miles home that was down to 43.
    Thats the problem comparing mpg figures. Conditions, driving style and traffic make a massive difference. Just too many variables.
    I have seen 53mpg on a fairly steady run and if I stop at services, which resets the reading and wipes out the crawl to the motorway the numbers can look great.
    2012 XF 3.0D S Premium Luxury

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