Why do automatic cars use petrol quicker?

[osprey]

This may be a silly question, but be kind to me as I'm not up on these things, but why do automatic cars use petrol at a quicker rate than manuals? I have had my Motobility automatic for 3 months now and have noticed that the petrol is being used far quicker than the manual car I had before. Please answer in a way that a 5-year old could understand and PLEASE do not go into the technical aspects of any answer in a too difficult manner for me to understand. Thanks in advance.

[Graham-W]

In general terms a manual will always, in theory, be more economical than an automatic. A manual transmission provides a more direct link via the manual clutch from the engine to the wheels while the automatic relies on oil pressure and a fluid flywheel as a clutch between the engine and transmission to supply the drive. There is always a loss of energy because of the automatic set up which makes the manual better regarding fuel consumption.

[dothawkes31]

I have driven automatics for 36 years and I understand what you mean, but there is a way of driving them economically, don't use the kick down for a start, and never accelerate away too fast, just be light on the acelerator, I also tend to take my foot up when i am on the motorway or doing 40plus and it doesn't hurt the speed guage never reduses, I don't mean take it right off the accelerator, just ease up a bit. I havea peugeot 306 V reg and i get about 32 - 34 mpg out of it.

[Panic Button]

A human can select the gar that will be needed, while an automatic selects the gear that was just needed. The manual is therefore operating more efficiently.

[R1Geezer]

It's also worth noting that the disparity is especially noticable in smaller auto cars.

[Seafarer1966]

Echo what DotHawkes says. Automatics can be good on fuel but you need to drive them gently. I prefer manuals. Mind you automatics don't have clutches which in my case over the years have been expensive to replace.

[Panic Button]

Automatics get through the brake pads quicker - you have to use the brakes more as there is much less engine braking.

I can usually spot an automatic by the number of times the brake lights keep coming on.

[dothawkes31]

I'm actually guilty of coasting alot to avoid over using the breaks, i know it's wrong especially if there is a car behind that can't tell i am slowing down and so i'm not reckless but it does make a difference.

[MarkRae]

> automatics don't have clutches

??? Of course they do! Just not manual ones with pedals:
http://auto.howstuffw...atic-transmission.htm

[Panic Button]

Don't apologise Dot!

If you are coasting in gear, not using the brakes you are driving economically and in an environmentally friendly way.

[dothawkes31]

I was going to say that i know they have automatic clutches! I don't know how it works but it does, mine also has low gears to select and they are useful in traffic.