Best MPG for cruising @ around 100-120mph
Discussion
I've noticed recently that a lot of people do appear to pootle along slowly, under the speed limit a lot with the occasional person in the outer lane doing well in excess.
This combination is quite annoying for those who want to make good progress safely.
I also wonder how some drivers manage to keep thier license when I regularly see people cruise through speed cameras at 10/20/30mph or more over the limit.
I wonder whether most cameras are just there to deter people from excessive speed and are set quite high to catch the real abusers.
This combination is quite annoying for those who want to make good progress safely.
I also wonder how some drivers manage to keep thier license when I regularly see people cruise through speed cameras at 10/20/30mph or more over the limit.
I wonder whether most cameras are just there to deter people from excessive speed and are set quite high to catch the real abusers.
I will cruise regularly in my Jag XFS between 115-125mph and achieve about 30mpg true as opposed to the display showing 35, any change upwards and my display has been known to go down as far as 18mpg! So much for diesel economy eh!? 
Oh and I am currently living in Germany so clearly the above figures are on the Autobahn!
Oh and I am currently living in Germany so clearly the above figures are on the Autobahn!
Edited by zx10ben on Tuesday 14th September 10:27
Interesting question. On my recent trip to Berlin from Vienna and back again I managed to get 48mpg in my 116d. Granted the roads through the Czech Republic where crap, but as soon as I hit the German border I kept my foot planted and averaged just a tad over 200kph. (It was 2am when I arrived in Germany and the roads were spectacularly clear between Dresden and Berlin).
My measly 116d managed an almighty 26mpg on those roads so a little better than some of the cars stated. I was also very proud to manage 219kph (indicted by TomTom going down a hill and probably with the wind behind me - (235kph on the speedo!
), although I wasn't looking at the MPG at that time... 
My measly 116d managed an almighty 26mpg on those roads so a little better than some of the cars stated. I was also very proud to manage 219kph (indicted by TomTom going down a hill and probably with the wind behind me - (235kph on the speedo!
), although I wasn't looking at the MPG at that time... I'd have thought a current 318D, 320ED or Passat Bluemotion or how about an old Honda Insight?:
http://www.evo.co.uk/carreviews/evolongtermtests/1... (may feel a bit flimsy by comparison!)
http://www.evo.co.uk/carreviews/evolongtermtests/1... (may feel a bit flimsy by comparison!)
All those arguing along the lines that doubling the speed takes 4 times the power seem to be forgetting that you are also travelling twice as quickly.
So in very simple terms, if a car gets 60 mpg at 60mph, then it would do about 30 mpg at 120. It's using 4x the fuel in a given period of time, but also traveling 2x the distance in the same time, so the overall result is roughly half.
So in very simple terms, if a car gets 60 mpg at 60mph, then it would do about 30 mpg at 120. It's using 4x the fuel in a given period of time, but also traveling 2x the distance in the same time, so the overall result is roughly half.
edo said:
champ54321 said:
I would say a larger engined diesel; 325d/330d
Dont rule out the newer 20d engines. Below is a screen shot after 1500 miles - some of which was allegedly done at significantly more than the OP's cruising speed. Half of it we had 2 bikes on the roof mounted vertically on bike racks which crucified the economy. Despite all this we still nearly managed 40mpg...
Conversely, a similar stint in my Evo last year got me about 12-13mpg and a good couple of hours spent when I got home washing out all of the yellow stains of unburnt fuel from every nook and crevice on the tail!
Edited by The Wookie on Tuesday 14th September 11:04
busta said:
All those arguing along the lines that doubling the speed takes 4 times the power...
Are wrong because it is eight times (if we just take aerodynamic drag into account)http://www.pumaracing.co.uk/TOPSPEED.htm
Have to agree, at this speed the energy you are using to force the car through the air is huge. If you care about mpg at all, drive slower.
A moderately powerful diesel barge is best. It needs enough power not to be breaking a sweat at 120, which lots will. Any modern 6 cylinder TDI should do, in a large car, since weight doesn't matter at this speed.
A moderately powerful diesel barge is best. It needs enough power not to be breaking a sweat at 120, which lots will. Any modern 6 cylinder TDI should do, in a large car, since weight doesn't matter at this speed.
Edited by LayZ on Tuesday 14th September 11:16
Given the right road, the right time of night and a car to do 120mph safely then theres plenty of opportunities to do this speed regulaly without endagering anyone else or getting done by Plod.
I know someone who had a last generation vectra cdti 150 who could get very high 30's/ low 40's doing over a ton.
I know someone who had a last generation vectra cdti 150 who could get very high 30's/ low 40's doing over a ton.
Steameh said:
A random question, but at 100+ would wind play a more important role in MPG?
e.g a strong headwind be more detrimental to MPG than travelling at say 60mph.
It would, remember TG a little while ago and James May's symopsis of how a car enters wind barriers at speed. I.e at 100mph it's like ploughing through cow dung, and 200 mph it's like ploughing through mud opr something like that, can't exactly remember. But I think what the point here is that it isn't a cumulative scale relative to hw fast you are going.e.g a strong headwind be more detrimental to MPG than travelling at say 60mph.
frosted said:
Air resistance is what kills mpg
At those speeds and providing you're cruising at a pretty fixed rate, yes.At low speeds with lots of stop/start acceleration, weight dominates.
That's why a large heavy car with a low drag profile could well return better fuel economy than a 1.2-litre diesel hatchback once you're cruising.
zx10ben said:
y2blade said:
Trommel said:
zx10ben said:
I will cruise regularly in my Jag XFS between 115-125mph and achieve about 30mpg
I think that's fairly impressive.
I'd like to see what mine does at 120mph on cruise
160kph on cruise and thereafter I take control.....
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