I've always slotted my car of the moment into top (or fifth gear) just as soon as the engine's torque allows. I've contented myself that the lower revs will aid economy, but I may possibly get a bit of plug sooting (I tend to drive old cars). I guess I compensate for this as I'm not afraid to use revs to overtake / get clear of traffic / etc.On balance it seems to work, but I'm now driving a newer car with electronic-shutter controlled intake length, antiknock sensors etc etc. It's a 2.0 litre V6, and while the power is a bit peaky, I find I can keep the car in fifth and drive almost like an auto - it'll easy (though not quickly) pull away from 1000 revs without complaint.Am I kidding myself? Is the antiknock gubbins just retarding the ignition so much that it's really inefficient at these times? Am I likely to gain nothing in mpg simply because of that?Just curious about others' thoughts on this. I'm not bringing "appropriate gear for the circumstances here" as it's hardly likely that a driving instructor would approve of me loafing around in fifth everywhere.

With an engine such as this- i.e. one with not alot of torque until quitehigh in the rev band, you might well find that getting staying in 3rd / 4thuntil you have more revs on the clock will be better for mpg.Our 2 litre 20v Volvo certainly was better on fuel to stop in 4th untilabout 55-60mph.Tim..

Fifth gear abuse?

Feb 18, 2005 22 Replies

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DocDelete 21 years ago

snip

Hmmm - I'm inclined to think that the oil system (if in good fettle) is designed to offer certain minimums at slightly lower than idle speed. There's either a useful oil film thickness there or not - I doubt the middle ground is particularly wide. This is just intuitive reasoning, and someone more qualified is welcome to chime in...

snippetysnip

S'very interesting. And you've clearly investigated this in depth!

On my next tankful of petrol I'm going to use the gears more, and drive like my wife a bit (hang in third until 38mph) - and I'll see if *anything* happens to the consumption ;-)

Cheers all - interesting stuff!

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DervMan 21 years ago

You mean the next twenty tanks? :)

For the next stage I need to bring a laptop running Windoze, since this can log more than two inputs...

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Rv! 21 years ago

electing not to

and bulbous knees

most comfortable

Actually they prefer to find a preferred RPM for their legs and stick to that as it gets the best effect from the lungs and muscles (or shoud that be petrol and gears?).

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So in effect the cyclist is getting best efficiency by sticking to a pretty fixed RPM (narrow band) just like your car does.

Rv! Sorry for the very late post.

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