most economical speed for a diesel van

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Mon 19 Jun 2006 23:57
most economical speed for a diesel van - metso
Hi I have a Ford connect, T220, Diesel, and do 120miles a day....mostly on motorways...I was wondering what is the most economical speed I should try and maintain , to save on fuel.

Thank you
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Tue 20 Jun 2006 00:34
most economical speed for a diesel van - Civic8
Check what the handbook says on it,usually accurate to 20% or more,motorway work would also depend on road surface/weather conditions/traffic.

So its not likely anyone can give real figures on this,but possible decent figure would be 65mph which is usually an in between figure depending on above-and whether you can hold the speed without getting bored ?
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Steve
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Tue 20 Jun 2006 07:10
most economical speed for a diesel van - Armitage Shanks {p}
There was a long discussion on this about a year ago, in this forum. Broadly speaking optimum fuel consumption occurs when the engine is running and the rpm at which max Torque is produced. In my diesel the handbook gives an rpm figure which equates to about 65 mph, which is the figure steve.o has come up with, although ti will obviously vary from make to make and with engine capacity.
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Tue 20 Jun 2006 07:12
most economical speed for a diesel van - Armitage Shanks {p}
Here is the link

www.honestjohn.co.uk/forum/post/index.htm?t=5733&v...f
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Tue 20 Jun 2006 08:23
most economical speed for a diesel van - Manatee
The engine might (or might not, I don't know) be more efficient at peak torque, but that would necessarily mean better mpg. At 56mph there is 25% less drag than at 65mph, other things being equal, and it's unlikely that you'll get worse mpg at the lower speed in top gear. If I have time in hand I became a truck at 56mph, and the mpg shoots up compared with 70 (I drive a somewhat van-shaped car).

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Tue 20 Jun 2006 10:09
most economical speed for a diesel van - L'escargot
The best economy is achieved at the lowest speed and smallest throttle opening in the highest gear possible ~ without letting the engine labour of course. It helps a lot if you anticipate what the traffic in front is going to do (that's in the unlikely event that you drive faster using these criteria tnan the traffic in front!) so that you use the minimum of braking.
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L\'escargot.
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Tue 20 Jun 2006 11:46
most economical speed for a diesel van - Number_Cruncher
Yes, I think that both AS and Manatee make valid points. Near maximum torque, the engine is producing the most power per unit fuel burnt per unit time, but, owing to aerodynamics, the power, and hence rate of fuel burn you need goes up rapidy with increasing speed.

If these were the only inputs, then I think L'escargot's view of slow, high gear, small throttle openings is right, but, you also have to include how much you value your time - this means that the optimum speed is different for everyone!! Students can happily sludge along without a care, while pensioners, for whom every last second is vital, could be steaming down the fast lane, as quickly as they dare!

Number_Cruncher
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