dont yawn - another mpg question!

[andycook]

went to Edinburgh and back at weekend.

24ish mpg on way down crusing at 70mph (but steady acceleration)
and on return

27ish mpg - but cruising at 60 mph

is it normal to see 3mpg drop for difference of 60 vs 70 mph crusing speed??!

on the subaru i only get that for a 25mph speed difference

[BUSHWHACKER]

The optimum speed for maximum economy is 56mph.....apparently

[Chillitt]

The optimum speed for maximum economy is 56mph.....apparently

probably cos at that speed you are bound to get a little push from a lorry..

[BUSHWHACKER]

No no, s'true. I've tried it in every vehicle i've owned, and it works, boring, but it works.

[TonyN]

Our 3.0 gets a huge difference cruising between 60 or 80. It's just hard keeping it less than 80, it keeps drifting up there if you not looking!

[DaveD]

Our 3.0 gets a huge difference cruising between 60 or 80. It's just hard keeping it less than 80, it keeps drifting up there if you not looking!

Thats what I meant in a prev post when I said respect to the guys who can keep her down to 65 on long runs.........mine seems to like the 80 85 figure (private roads of course)...

[nelliecat]

Not wishing to deflate anyone's ego but when you say 80 - 85 is that on the clock? If go I would suggest a run using GPS based speed measurement, as my Surf reads 80+mph on the clock when only doing 75mph on the GPS. YES I trust my GPS measurements more as I've had 3 differnet devices all running at the same time, and all agreed within .2 mph! So, if optimum speed is 56mph, is that TRUE or clock speed?

[BUSHWHACKER]

56mph GPS speed!
Or just under 60.

[Pete]

56mph GPS speed!
Or just under 60.

On my 2.4, when I was clocking 80, the speed according to the gps was 72!
Pete

[mud skipper]

The optimum speed for maximum economy is 56mph.....apparently

56mph/100kmh is supossedly most economical is something to do with gravitation pull versus drag or somthing like that so i was informed

my peugot van driven @ 50ish(very rare) does about45mpg
@80-90 (normal) its 28-31 mpg

surf i dont know i just fill it when needed

[FlySurfer - Edy.]

I've just noticed a drop from 25 mpg at 70 to 19.871342 mpg at 80 - 90.

[Draig]

sadly it's true - the faster you go the more petrol you use.


(and yes - there is a big difference between 60 mph and a decent cruising speed officer)


my speedo was spot on at 53 mph cos that's what my speeding ticket said too!

[Bikenuts]

The speed that gives best economy will vary a little according to gearing etc however it will usually be a little over 50mph as this is about the point when aerodynamic drag becomes the single most important factor. The CD (coefficient of drag) of a surf is appalling and the CD^ (coeficent of drag times frontal area) even worse so a small increase in cruising speed will make a big difference to your economy.

[da SLUG man]

i thought it was cos wen you're going UP north, it's more strain than going DOWN south!