Real world mpg

(17-02-2012 05:22pm)PhilSkill Wrote:  Not that I don't believe you but, If there's any start/stop that must be impossible! If I did 55mph in 6th reset the trip while doing that and stayed at that speed constantly almost rolling with no throttle I would not reach 50mpg! 40 something yes, but not into 50's.

agree philskill....max I have got at 65 over 200 miles is 40.7....not that good! so how he has got 50's?????

Mine is improving - managed to get 36 mpg on a the motorway at the weekend, and I was driving 70-80 mph and done some overtaking with all the gadgets on, so not too bad really. However as soon as you hit the town and do more urban driving - 14.7 mpg!

Pity about 75% of my driving in town/city/start/stop!

Honestly guys, I was quite surprised as well. When I first bought the car max I got was 40 mpg on a 300 mile trip so I was expecting something in the mid 40's . No speeding just stuck to speed limit slowed down 60/50 and there was no start/stop,some downhill and uphill it went down to 49 mpg.

You must have a golden engine or the trip is under-estimating! Have you done a real calc? As you'll see from my graph I got 29mpg first tank! What the dealer gave me in the tank barely got me home! Im hoping the weather warming up will improve the mpg too, always 4-5deg cooler in the sticks compared with London! Plus theres a few hills around me!

Good news is ... Milder weather with no cold starts boosts my average by 10%, from 33 to 36 mpg (that's for a SD4 auto 5 door, mixed 50/50 town/country).

In theory cold weather doesn't have much effect on diesel economy - no concept of a richer fuel mix like there is in a petrol engined vehicle. In fact cold/dense/damp intake air actually goes towards producing a bit more power....

Running around with heated seats/screens on etc won't help though - electrical load makes the alternator harder to turn so acts like a brake on the engine....

Not once fully warmed up for sure, but in colder weather takes longer to get up to temp. Diesel requires heat and pressure to ignite (hence the initial glow plug heating) so guess while the engine is cold it's less efficient.

My current diesel gets 46mpg in winter, 52mpg in summer. Same driving, same figures every year. My petrol cars show my variation and usually MUCH closer to official mpg figures.

(17-02-2012 03:33pm)ChuckieB Wrote:  Just announced on the radio. Diesel tipping over the £1.43 mark. Disaster!!!![/u]

(18-02-2012 02:37pm)Asty Wrote:  My current diesel gets 46mpg in winter, 52mpg in summer. Same driving, same figures every year. My petrol cars show my variation and usually MUCH closer to official mpg figures.

It must be a function of the proportion of the amount of the total driving distance done from cold versus the amount of sustained driving with the engine at normal working temperature. A diesel engine will be less efficient in cold weather from a cold start, but will be more efficient in cold weather when warmed up. Therefore, if you do lots of short journeys you'll be worse off in winter, if your journeys are fewer but long, better off.

You should always also take into account winter diesel is a different mix compared to summer fuel in order to prevent diesel waxing up. Think this usually changes from November through to Feb, making it less economical.