Fuel Consumption And Cruise Control

[puternut]

Greetings

Until recently I was always lead to believe that cars with automatic gearboxes used more fuel than manual. I was told many years ago to expect 10% less in an auto. Apparently not.

Last year I changed my Mobility car to a Vauxhall Meriva which according to the brochure gave greater mpg in auto than manual. OK I'm not going to assume the figures quoted are correct but on checking a few other makes they all claim this does appear to be true.

My real query though is the use of the cruise controls. Due to circulation problems in my lower legs I thought I would give this a try and believe me it has been a godsend especially on the longer motorway journeys.

Do you think that using the cruise control in all situations - including urban - will improve the m.p.g. or not? Personally I am unsure as it seems to me that on even low angle descents seems to change gears down but on similar gradients up it remains in the higher gear.

Would the fact that I have a diesel engine - my first in over 40 years motoring - affect it?

[shoota]

A very complex question........

[shoota]

Auto gearboxes nowadays are much smoother and efficient than they used to be so the mileage 'gap' has decreased if not diappeared altogether.
Does your Meriva not have a minimum speed that the cruise control would work at? Mine won't operate unless the car is doing 40 or over (I think) which obviously makes it unusable in towns. Also (IMO) it would not be wise or safe to do so.
But theoretically as the cruise control would select the most efficient gear to maintain the desired speed I can see that it might improve fuel economy in an auto car but not necessarily in a manual car where it is incapable of influencing the gear selected.
Just thinking - I'm not an expert!

[FredPuli43]

Maybe they've improved recently, but I always found cruise control a damn nuisance. I find it impossible to drive in the UK without touching brake or accelerator, at which point the control switched off.

Modern automatics, with the computer control and a box which is essentially electric, unlike the old Borg Warner type with lots of hydraulics, is every bit as efficient as any manual box. You'd need to be an exceptional driver to pick the perfect combination of speed and gears to match what the computer does

[puternut]

Cruise control is usable at 20mph or more

[Hopkirk]

Fred, in my experience, touching the accelerator doesn't switch off the cruise control.

[sigma]

I wouldn't use cruise control in an urban environment. It is ideal for motorway journeys where a constant speed is used over a long distance or period of time.
If you have trouble with your legs it might be worth having a hand control fitted to operate the accelerator.

[TWR]

Cruise Control, Motorways mainly, regards fuel consumption, that depends on your driving habits, " Not having the car to labour, necessary gear changing, changing at the correct time, Tyre Pressures, Roof bars / racks, head wind, all contribute to excess fuel consumption, the company I used to work for had devices fitted to make sure the HGV changed at the correct time, rev, it did work, it also helped as we were driving tankers.

[Baldric]

Do HGVs have cruise control TWR?

[TWR]

Yes, I though YOU would have known that!

[Hopkirk]

The modern digital tachos can report back how much you use the cruise control on an HGV.

If you don't use it enough the employer will complain, as they are better than humans at driving economically.

[TWR]

This depending on your experience & conditions.

as they are better than humans at driving economically.

[Toureman]

As you have now got a diesel that is why the MPG is a lot better!

The Cruise control will change down gears going down hill to stop you going faster, thats why it's called cruise control.

The cruise control only saves a little of your MPG.

[Mass_Hysteria]

Surprisingly, having the Air Con off increases your mpg, well it does on mine, Focus 1.6 tdci (not auto)

[FredPuli43]

I find that going downhill with my cap on backwards works best. (A tip I got from the Veteran Car Club)

[DTCwordfan]

Aircon can cost up to 10% of your mileage/litre when running medium-hard.

[Hopkirk]

Leaving your air con off and opening a window instead can increase your fuel consumption too.

[tali1]

Cruise control is only good on long straight runs -such as m/way.Avoid on gradients and elswhere

[Old_Geezer]

Cruise control is great for cruising down the motorway, but is simply a pain where you are forever putting it on and then taking it off in urban driving. It's not designed for that. Probably not worth the hassle trying to squeeze the most from it like that. Can't be that keen surely.