Most economical speed?

[Ry_B]

Growing up I remember reading loads that the most economical speed is 56mph, but this may have just been that trucks etc are limited to that?

I know it will vary from car to car oviously, but say if you were on a perfectly straight road in a perfectly average family car, will 60mph be the best speed to travel at for the most miles travelled with the least petrol used?

[ludicrous speed]

Ry_B said:

I know it will vary from car to car oviously

[B'stard Child]

Ry_B said:

I know it will vary from car to car oviously,

Right it will and things like gearing etc play a huge part

For a manual car

I'd say it would be the lowest speed that any car was happy to pull along at in the highest gear (so lowest rpm, smallest throttle opening for the given speed and lowest aero drag)

For an Auto

The lowest speed where the lock up is engaged

Edited by B'stard Child on Thursday 14th October 19:18

[Ry_B]

Must be an average though for say a 2 litre petrol car? Or a 1.9tdi? Where you can make the most progress where your car is slipping through the air without causing too much drag to hinder economy

[Strawman]

56-57 mph, for almost all cars. Partly down to manufacturers trying to get good results in the official MPG tests.

Edited by Strawman on Thursday 14th October 19:19

[twazzock]

100-120mph

[frosted]

Which is 56 mph , unless you have a momaro then you can be doing 120mph at just over 1k rpm ( apparently )

[Ry_B]

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Just found that thread

[B'stard Child]

Ry_B said:

Must be an average though for say a 2 litre petrol car? Or a 1.9tdi? Where you can make the most progress where your car is slipping through the air without causing too much drag to hinder economy

Why must there be an average!

It won't be 56mph thats for sure in most cars

[snuffle]

B'stard Child said:

Ry_B said:

Must be an average though for say a 2 litre petrol car? Or a 1.9tdi? Where you can make the most progress where your car is slipping through the air without causing too much drag to hinder economy

Why must there be an average!

It won't be 56mph thats for sure in most cars

the 1.9 will use less petrol

[B'stard Child]

Ry_B said:

http://www.pistonheads.com/gassing/topic.asp?h=0&a...

Just found that thread

Ahh so looks like sub 30 for most cars - and then you are going to be a PITA for every other road user outside of a town

[B'stard Child]

snuffle said:

B'stard Child said:

Ry_B said:

Must be an average though for say a 2 litre petrol car? Or a 1.9tdi? Where you can make the most progress where your car is slipping through the air without causing too much drag to hinder economy

Why must there be an average!

It won't be 56mph thats for sure in most cars

the 1.9 will use less petrol

I see what you did there - should have said none

[bazking69]

B'stard Child said:

snuffle said:

B'stard Child said:

Ry_B said:

Must be an average though for say a 2 litre petrol car? Or a 1.9tdi? Where you can make the most progress where your car is slipping through the air without causing too much drag to hinder economy

Why must there be an average!

It won't be 56mph thats for sure in most cars

the 1.9 will use less petrol

I see what you did there - should have said none

A 1.9TDi running on petrol won't be very economical at all my the time the AA have drained it all after less than a mile of driving...

[saaby93]

You lot do have a laugh sometimes

[SClarke]

On an average road in an average car the most economical speed to drive would be..... 0 mph. I guarantee you won't use a drop of fuel for hours on end.

[Speed_Demon]

SClarke said:

On an average road in an average car the most economical speed to drive would be..... 0 mph. I guarantee you won't use a drop of fuel for hours on end.

Fu beat me to it.

[Stedman]

B'stard Child said:

Ry_B said:

Must be an average though for say a 2 litre petrol car? Or a 1.9tdi? Where you can make the most progress where your car is slipping through the air without causing too much drag to hinder economy

Why must there be an average!

It won't be 56mph thats for sure in most cars

My car isn't far sure. Much happier at 100 65-75.

[tomwoodis]

Funny, I was thinking the same thing today.

Guessing this must have changed overtime. A lot of cars now have a 6th gear for a kick off, that must change things quite a bit but I'm guessing it won't be that much greater than it used to be because air friction ain't changing no matter how technology moves on!

I came to the conclusion that it will be different for every car, the biggest factors being the amount of drag that your particular car experiences as it passes through the air, the number of gears it has and the relative gearing of those gears i.e how high is the engine having to rev In top gear at a particular speed.

I guessed something like 60mph would be pretty good for my 3.0 z4 in top gear seeing it is just ambling along rev wise and the air resistance doesn't seem too harsh at that speed given the cars relative shape.

That sound about right or am I being overly hopeful?

[anonymous-user]

136.6887 mph for all cars. I used complex maffamatix to work this out. Dont question my ability.

[Alfanatic]

Speed_Demon said:

SClarke said:

On an average road in an average car the most economical speed to drive would be..... 0 mph. I guarantee you won't use a drop of fuel for hours on end.

Fu beat me to it.

0mpg is not the most fuel efficient result. Even if the engine isn't running, you're getting 0 miles from the gallons of fuel sitting idle in the tank.

If, however, you push the car to its destination, then you'll hit the magic 0. Unless cornish pasties come by the gallon.