Fuel prices: how to save £500 a year (even if it does mean driving at 20mph)

[recycled]

is it against the law to drive at 20mph all the way to london on the M62/m6/m1 or M40 ?

 

[Bobby Dazzler]

Anyone technical about? I've been trying this 'drive at 40 or less' advice during the fuel shortage (and lots of the roads through the New Forest are 40 mph so easy to do for quite long distances)

For me it does not appear to reduce fuel economy . The reverse in fact. I get more if I go where I can do about 50 or 50-60 mpg.

Could it be in the zone where you're switching gears as your speed increases and decreases.

I suspect above 50mph, you'd remain in top unless accelerating with a little vigour?

 

[dsolds]

Could it be in the zone where you're switching gears as your speed increases and decreases.

I suspect above 50mph, you'd remain in top unless accelerating with a little vigour?

Plus of course most auto's don't actually pull top gear until at least 50mph. My E500 is most economical at about 58. 58mph on a motorway never sees less than 34mpg wheras 40mph on an A road gets about 27mpg. Even a steady 70mph gives over 30mpg. Beyond that I don't know as most of my driving is on works time so I stick to the limits.
Perhaps manual gearboxes which permit top gear to be maintained at 40mph are more fuel efficient but surely the engine would be labouring at such low rpm.? Very confusing indeed for a simple soul like me.

 

[Dragon]

I was getting 75mpg @ 50mph on the way into work in the wifes D5 today.

What car is this YZE850Z ?

 

[Dragon]

I went on an excursion to Harrods on Sunday and got 37 mpg driving at 65mph on my slk200K. That 22 litres for 232 miles with the roof folded away.:bannana:

 

[Sp!ke]

What car is this YZE850Z ?

Well its a strange mixture with all the fast bits including the rather heavily modified engine taken from this.

shoehorned into this. It's now a dirtbike capable of 140mph

The idea being to make something similar to this rather unaffordable piece of exotica below.

To keep the thread on topic, On the way back from work today (30 miles mixed driving inside the M25) I averaged 59mpg. I found that any less than 40mph and the auto box dropped gears making revs rise above 1800rpm and fuel economy suffer.

Will see what happens if I over ride the gearbox using geartronic next time wifey lets me play with her new toy.

 

[Shude]

Plus of course most auto's don't actually pull top gear until at least 50mph.

If I just tickle the gas pedal and the engine temp is 80 degrees then mine will happily shift up to 5th gear at around 30mph. It doesn't take much pedal movement to get it to change again though.

 

[dsolds]

If I just tickle the gas pedal and the engine temp is 80 degrees then mine will happily shift up to 5th gear at around 30mph. It doesn't take much pedal movement to get it to change again though.

Ah yes, forgot that.....Mine's the 7g-tronic thingy. More gears than you can shake a stick at and it's never in the right one !!
But the 5 speed boxes would be in top at lower speeds...although I would have thought the actual ratio in top would be the same (or thereabouts), just that there's a couple more in between.
Any Merc mechanics care to comment?

 

[st4]

I tend to keep mine below 2k revs so stick to 60 on mway and 55 on A roads. See's the E climb to 51mpg

Diesels tend to be @ their best MPG wise below 2k revs.

 

[Shude]

Ah yes, forgot that.....Mine's the 7g-tronic thingy. More gears than you can shake a stick at and it's never in the right one !!
But the 5 speed boxes would be in top at lower speeds...although I would have thought the actual ratio in top would be the same (or thereabouts), just that there's a couple more in between.
Any Merc mechanics care to comment?

I would suggest that the difference is quite small as to whether you are in 5th, 6th or indeed 7th at 30mph

If you know which gear it is in then try asking it to change down and see how much difference it makes to the RPM at the speeds you are talking about.

 

[Shude]

Technically it does work and apart from the lack of forward visibility it is fairly safe.
You can really feel it in an un aerodynamic vehicle like a LandRover.

I used to work with a guy who had a mini a long time ago with a big aerial on it. He said the aerial would whip around on the motorway but if he literally tailgated a truck it went still. He reckoned he could practically turn the engine off and coast the rest of the way but he had to be sharp with the brakes . I know he was joking but there is some truth in what he said; this is why trucks are often seen on the motorway, slipstreaming or as the yanks would say "drafting" in close formation in order to reduce fuel consumption.

 

[Dieselman]

or as the yanks would say "drafting".

Isn't that what Grav does after a few pints of Fosters?

I tried this technique last Sunday as I had something on the roof making a lot of wind noise. It really worked.

Been into town today at both rush hours today and scored 55mpg this morning and 52mpg this afto with A/C on. Not bad I thought..but not in a Merc though..

 

[Bobby Dazzler]

I did a 280 mile round trip today, M42/M40/M25. Had cruise control set to 70mph all the way and managed bang on 32mpg (calculated based on fill to fill).

I thought that was pretty good for an ML.

Was a good run too, apart from the puncture on the M25 near Heathrow!!

 

[MBManInKen]

Was a good run too, apart from the puncture on the M25 near Heathrow!!

So, the 32mpg was on the back of a flat bed?