Gear selection for economy

[FiF]

At last another sensible post on the thread by someone who understands the concept of flexibility in the right gear and the link with planning and ability to vary speed up and down easily. Also agree that there are some posters either on the wrong forum or who would benefit from some education.

[Strudul]

FiF said:

At last another sensible post on the thread by someone who understands the concept of flexibility in the right gear and the link with planning and ability to vary speed up and down easily. Also agree that there are some posters either on the wrong forum or who would benefit from some education.

Or another post by someone who doesn't understand what the word "economy" means.

I know this is PH, so you feel compelled to pick apart any point and probably diagnose OP with some medial condition, but:
- a higher gear is more fuel efficient most of the time
- cars are geared differently, with different power levels, so blanket statements about specific gears are stupid
- flexibility is irrelevant to fuel efficiency
- 99% of the time, you don't need a flexible gear
- if you were any good at driving, you'd be able to downshift when needed

[FiF]

Strudul said:

FiF said:

At last another sensible post on the thread by someone who understands the concept of flexibility in the right gear and the link with planning and ability to vary speed up and down easily. Also agree that there are some posters either on the wrong forum or who would benefit from some education.

Or another post by someone who doesn't understand what the word "economy" means.

I know this is PH, so you feel compelled to pick apart any point and probably diagnose OP with some medial condition, but:
- a higher gear is more fuel efficient most of the time
- cars are geared differently, with different power levels, so blanket statements about specific gears are stupid
- flexibility is irrelevant to fuel efficiency
- 99% of the time, you don't need a flexible gear
- if you were any good at driving, you'd be able to downshift when needed

Understand fully what the word economy means. 99% of what time? All driving all roads? On whatever road you need to be in an appropriate gear, if the conditions are such that steady state speeds are predominant then that results in a different plan and gear selection that in, say, a 30, where expected conditions are that frequent changes of speed may be necessary, and the ability to do this without the need to change gear is preferable in my opinion and that of others.

If you took the trouble to read what written earlier you will find that I commented that the advice from the SAC was not quite correct, instead of being dogmatic, oh should be in X gear in a Y limit, and being specific about the revs it really should be think about it and figure out what is best for your vehicle in various situations having consideration to various demands, including flexibility of speed up and down and not just economy above all else. If you don't agree or get that, then frankly I don't see the point of continuing.

[Strudul]

FiF said:

Understand fully what the word economy means. 99% of what time? All driving all roads? On whatever road you need to be in an appropriate gear, if the conditions are such that steady state speeds are predominant then that results in a different plan and gear selection that in, say, a 30, where expected conditions are that frequent changes of speed may be necessary, and the ability to do this without the need to change gear is preferable in my opinion and that of others.

If you took the trouble to read what written earlier you will find that I commented that the advice from the SAC was not quite correct, instead of being dogmatic, oh should be in X gear in a Y limit, and being specific about the revs it really should be think about it and figure out what is best for your vehicle in various situations having consideration to various demands, including flexibility of speed up and down and not just economy above all else. If you don't agree or get that, then frankly I don't see the point of continuing.

If you understood "economy" we wouldn't be discussing this.

SAC states that 3rd gear is the most fuel efficient at 30mph
1) It probably isn't for 99% of cars
2) 3rd gear isn't the same in every car
3) Flexibility as a justification is moot

Road speed limits don't dictate fluctuations in speed, traffic and road layout does, but even so, my car will happily accelerate from 24mph in 5th - not as quick as in 2nd / 3rd / 4th, but enough to keep up with traffic. Also, chances are, if you are changing speed in a 30, it's for traffic lights / junctions, where you will be dropping to 1st / 2nd, so the "flexibility" of 3rd is pointless. Moreover, as above, the SAC statement and thread is about maximising fuel economy, so flexibility is irrelevant.

It's like discussing the most practical car, then suggesting a TVR. Yes, it maybe faster and better at many things, but that's not the point of the discussion.

[FiF]

Shortish words, simply put. I understand what economy means, just that it's very low in my priorities when making a plan.

[Strudul]

FiF said:

Shortish words, simply put. I understand what economy means, just that it's very low in my priorities when making a plan.

And that's perfectly fine, I'll drop a few gears when I want to have fun, but not really appropriate in a thread about optimising it.

[rainmakerraw]

Strudul said:

If you understood "economy" we wouldn't be discussing this.

SAC states that 3rd gear is the most fuel efficient at 30mph
1) It probably isn't for 99% of cars
2) 3rd gear isn't the same in every car
3) Flexibility as a justification is moot

Road speed limits don't dictate fluctuations in speed, traffic and road layout does, but even so, my car will happily accelerate from 24mph in 5th - not as quick as in 2nd / 3rd / 4th, but enough to keep up with traffic. Also, chances are, if you are changing speed in a 30, it's for traffic lights / junctions, where you will be dropping to 1st / 2nd, so the "flexibility" of 3rd is pointless. Moreover, as above, the SAC statement and thread is about maximising fuel economy, so flexibility is irrelevant.

It's like discussing the most practical car, then suggesting a TVR. Yes, it maybe faster and better at many things, but that's not the point of the discussion.

If you read the OP, the SAC didn’t say anything about economy. The OP had a conversation about whether 3rd or 4th was more suitable for town limits. Fuel economy didn’t come into it. That came later from the OP himself.

[rainmakerraw]

The OP said:

I recently did a speed awareness course, and one of the guys running it was conducting a conversation about gear selection. I suggested that 4th gear was perfectly suitable for a 30 mph limit whereas he said 2nd at 20, 3rd at 30, 4th at 40 and 5th at 50. I pushed him as to why 3rd at 30 was better than 4th and his answer was "it's a more flexible gear,

Apologies for the double post, it’s hard to mess with multiple quotes on mobile.

[Strudul]

rainmakerraw said:

If you read the OP, the SAC didn’t say anything about economy. The OP had a conversation about whether 3rd or 4th was more suitable for town limits. Fuel economy didn’t come into it. That came later from the OP himself.

From personal experience, fuel economy was explicitly stated in the SAC, which I don't believe will be an isolated incident.

[FiF]

Strudul said:

rainmakerraw said:

If you read the OP, the SAC didn’t say anything about economy. The OP had a conversation about whether 3rd or 4th was more suitable for town limits. Fuel economy didn’t come into it. That came later from the OP himself.

From personal experience, fuel economy was explicitly stated in the SAC, which I don't believe will be an isolated incident.

Just as a side observation, when I did my very first advanced course, which was a foreign nation's equivalent(ish) of the then UK class1/2 advanced but with different add on packs, e.g. winter ice driving techniques, then fuel economy was not considered. Today, or at least on my last refresher, it was considered within the syllabus, but you were never expected to compromise the basic tenets in the interest of economy.

[waremark]

Strudul said:

From personal experience, fuel economy was explicitly stated in the SAC, which I don't believe will be an isolated incident.

I have attended 2 SACs. My instructors didn't say stuff which was incorrect. You were unfortunate. None of us here believe that 3rd will be the most economical gear at a steady 30 in many cars.

[Wooda80]

It's a Speed Awareness Course, not an Fuel Economy Forum.

They'll give attendees advice to help them stay within the speed limits.It will be simply put to help those who who are not particularly interested or skilled in driving.

You may feel that the advice given is beneath you.

I'm sure that if you explain that you have subscriptions to several motoring magazines,and Expert level on several forums, that the course leader will be impressed and give you a special exemption. If you are prepared to share your spreadsheet of road speeds and engine speeds in your Peugeot then he will be minded to use then in future courses, just make sure you insist on appropriate credit.

[bobble293]

"It's a Speed Awareness Course, not an Fuel Economy Forum..."

Absolutely! And unless a person's very selfish, safety trumps economy every time, or ought to. I've been driving for 50 years, and passed my advanced with the IAM 20 years ago. I was hurt by my initial assessor's summation of my demonstration to him of my mastery of my vehicle. "How have you lived this long..."
It was food for thought. After completing the course and passing the test observed by a police class 1 driver, I found I wasn't quite so busy behind the wheel, so could devote more of my limited cognitive abilities to observation, and management of hazards. Being in the right gear at all times is part of that. You can vary your speed within quite a wide range just on the throttle.

I've owned and driven eleven manual vehicles since passing the test, and found the suggested gear selections have been a constant, whether in my VW T4 vans (1.9 and 2.5) My Saab diesel 150 horse, Passat Diesel 1.9 110 horse, Vectra petrol 125 horse, Polo petrol, 75 horse, and Seat Ibiza 85 horse.
Third in a thirty zone allows you to drive through town, (traffic allowing) at thirty, losing speed down to fifteen or so, yet still not dropping out of the power band and thus being obliged to "drop a cog" to accelerate after passing a hazard. It's all part of the "System" of driving. People who claim they can't maintain the posted speed in any given area, whether it be 20, 30, 40 are almost certainly in the wrong gear.
Inclines, of course, make a difference. In third, you may be obliged to drop a gear to climb a steep incline, in fourth, you almost certainly will.

Round my way, there's a 25% down gradient with a speed camera (30 limit) on it. I descend in third, foot off the throttle, and both my current vehicles maintain the necessary speed. Other drivers have often, obviously, selected too high a gear, since they're on the brakes all the way down, causing unnecessary wear on friction material and discs.
(I'm not advocating "engine braking" but using the engine's resistance to maintain a speed, not to lose speed.) "Gears to go, brakes to slow"

On arrival at the NSL signs, leaving a thirty zone, in third, you're already set up to start scooting off up to the new limit without having to select a lower gear. As for economy, with my driving style old dinosaur Passat TDI used to return 42 MPG to 52MPG, the latter at motorway speeds. The Ibiza returns a regular 47 average, 50+ on longer runs.

Asking your engine to slog at low revs means the oil pump's running slow, too, delivering less oil while your mains and big ends are under more pressure. If my wife drove my Cooperised mini back in the eighties, I was appalled at how low her revs were, and how low the oil pressure was, too. A lower gear and a few more revs saw the pressure rise to something better...

[Strudul]

But in 5th I can happily go between 25 and 125...

I don't see why dropping a gear or 2 is such an issue?

What's the point in driving a manual if you never change gear?

If you can't change gear fast enough to react to something, should you really be driving a manual?

In 5th, my car will pretty much keep itself at 30 on the flat. In 3rd I'd have to press the pedal much further, and deal with a significantly more sensitive throttle response.

Downshifts are an excuse to blip the throttle.

What situations exist where you have to accelerate hard with zero warning?

Should slower cars be deemed unsafe and banned because they can't accelerate fast enough?

Acceleration at 70 in 6th isn't very quick, should I leave my car in 4th / 5th on the motorway?

[Eyersey1234]

My Fiesta will quite happily do 30 in 4th, I was always told not to use 5th at less than about 40-45 as it's designed for high speed cruising.

[Leonard Stanley]

Like this - https://www.facebook.com/GreatVideosTV/videos/1924...

[Evilex]

I just drive in the tallest gear possible.
My Fiat (diesel) develops 150 lb/ft of torque from about 1500rpm (allegedly)
It can easily hold 5th (top) downhill in a 30.
Uphill or flat I'd use 4th.

I get just short of 750miles from a 14.5 gallon (66l) tank, but of course it's dependent on the kind of driving I'm doing.

The best aids to economy seem to be to minimse acceleration, use engine braking (safely!) and select the longest gear the vehicle can comfortably withstand.

[catso]

Surely 'flexibility' means being in 3rd gear rather than 4th or 5th gives you more instantly available acceleration? - Is that what speed awareness courses are about?

I can't really see why they make such comments as it's car/condition dependent and got nothing to do with exceeding the speed limit, plus if you drive an auto then it's (normally) out of your control anyway - I think my car would likely be in 5th gear at a steady 30mph, why would I override that to be in 3rd?

[NickGRhodes]

Has anyone actually measured economy at 30, 40 50, 60 or 70 mph on a flat road in different gears ?

[DJ_AS]

NickGRhodes said:

Has anyone actually measured economy at 30, 40 50, 60 or 70 mph on a flat road in different gears ?

I'd like to know this too. My personal anecdotal evidence suggests the differences in economy may be small. I did a Ride Drive day several years ago in my Mondeo turbo diesel. Spent much of it charging around country roads in 3rd gear when I would normally have been in 4/5th for the equivalent speed (note, not going faster, just using a lower gear). We even spent an hour or so blasting around the track at Bruntingthorpe.

The car still averaged in the low 40's mpg vs a usual of high 40's. It would've been better still without the track time. My feeling was that higher engine speeds were being somewhat balanced by smaller, shorter throttle openings.

Edited by DJ_AS on Friday 20th July 16:20