30mph, manual box, 3rd or 4th gear.

Driving instructors here in Denmark have begun teaching new drivers to go all the way to 5th at 30-35 mph over the past 10 years, the argument being better fuel economy. But as Greg says, it depends on the car you're driving.

My girlfriend was taught to drive this way and while it worked great with the 1.6 litre gasoline VW Polo she had when I met her, the 1.9 litre diesel Skoda we have now struggles and uses more fuel in 5th gear at 30-35. 3rd is too low for that speed. The engine almost screams, so 4th it is unless we're going up a steep hill.

I've driven other cars that would almost die if you went into 4th at that speed and the same if you changed into 5th before doing 55-60 mph. It all depends on a lot of variables, like Greg pointed out.

Exactly.

Thanks for the conformation....
Recommendation "You should be in 3rd" BUSTED, its vehicle dependant?... that sounds good to me.

Had the same soddin' argument AGAIN.......

Its getting tiring, but this IAM starts on with the you should be in 3rd around town because it gives you better control of the vehicle....

Erm.... How?...

"Sudden" anything will confuse people, so thats out of the question, braking, we all have the pedal in the middle if you want to slow down, you argument doesnt hold water.....
This was being explained by a fellow driver, which got the retort "Well your not IAM..."
(Where IAM is Institute of Advanced Motorists...)
As if omy IAM's have the knowledge of such things?... this eso-exoteric argument is why I dislike IAM's and their like, they think they know it all.

So there I was expecting the toys out of the pram for being told he didnt have the qualifications to know what he was talking about....
No.
The reply was "Well, if a full stacked licence and 20 yrs driving is not enough for you, plus I hold ADI, I cant argue with you... my Wife says I shouldnt argue with idiots."
ADI is Advanced Driving Instructor, the ones who teach Heavy Goods.

My part in the argument was I argued that the gear should be as high as it can without stalling the vehicle, and if you can accelerate in 5th at 30, the car has enough power....

I was then told that put excessive strain on the engine.....

I dint know that one.
The strain put on an engine at top speed where you are fighting aerodynamics under full throttle is less than that then is it?...

I then argued that it should all depend on the vehicle, if the vehicle is a micro-engine that cant hold 30 in top gear and cant accelerate at all, perhaps you need a lower gear, or a better car.....

I left the argument at that point, as that ijurt drives a Micra, and we already had the argument that even though mine is a lot older, its a 5 seat plus luggage, and as I have a 5 adult size family, its much better than his 4-seat-and-a-handbag.


During that argument, I also heard the line that may need a screen wipe....
"You car can only get to 69 up that hill, therefore its bloody useless to me... "
"Why?... is that enough?..."
"No, I live at number 93...."

to give a more definitive answer, the engine should be turning as slowly as it can, while still having sufficient torque for reasonable acceleration and sufficient lubricant circulation.

as I said in a different thread - in my truck, 30 MPH in 2nd gear burns more fuel than 55MPH in 4th.

in some cases 30 MPH in high gear will push your engine below idle.

mine doesn't even HAVE 4th...

Solved that problem.

for the same reason spinal Tap's amplifiers go to 11.

For my car? Neither! 5th gear! 3th gear is for traffic circles only.


This depends on many factors, the amount of seats isn't one of them. It mainly depends on the gear ratio and many factors of the engine.

It's true, the lower the RPM (without much load on the engine), the more MPG you get. This is true for all internal combustion engines, the only difference is that a diesel engine can handle more load near idling RPM while still economic.
If you have a turbo, it's even more intense, high RPM make the engine even more inefficient.

The problem is that the slower the engine runs, the less forces the crankshaft can handle. There are two major effects, one is the slower oil pump so there is less oil pressure, the crankshaft floats on pressurized oil. The other effect are the gliding bearings of the piston rods. The greater the RPM, the more forces they can handle until the oil film breaks.

Sadly, most engines are not designed for high torque near idling speed. They suffer immense wear when at low RPM but full throttle. The manual of my car (if it is equipped with the classic grey cast iron 1.8l block) recommends driving 40kph or more in top gear (5th gear) and encourages to floor the accelerator instead of downshifting. The reason is that this engine block is also used for the diesel engine so it has an extra tough crankshaft and wider bearing blocks.

Most engines are not capable of tolerating full throttle near idle RPM, especially all the modern lightweight engines.




Most of those have no idea what they are talking about. My driving instructor insisted that the car speeds up when depressing the clutch while braking and didn't allow to flip the rearview mirror into the "night" position. He didn't belief that those are 2-in-1 mirrors where when you flip the lever, the reflection goes down to 20%. He claimed that he had cracked one open and couldn't find a second mirror inside. How could he, it's a prism! And there were many other things he had wrong.

The problem is that the original "driving instructor's text book" was written in the 1950s and never really updated.

I think the same is true for the rest of the world, too.

Here in Germany, the driving instructors also teach using 3th gear for 50kph (city) even if the cars originally came with a 3-speed gearbox, got 4 in the late 70s and 5 in the late 80s. Originally, teaching to use the 3th gear was meant to reduce unnecessary noise, they taught driving "slow" in top gear. Nowadays, 5th gear is the top gear but the driving instructors still insist using 3th gear.

Back then, cars had 3 gears and could reach speeds of around 120kph. Modern cars can reach 200kph and have 5 or more gears. It depends on the gear ratios which gear is correct for e.g. 30kph, but in most cases, it's at least 4th gear.



Careful, even if the engine is strong enough, that doesn't mean it can tolerate the abuse as I had explained above!

Again I had another argument on this subject.....
So I am wanting some kind of test done.
So time to try and make this into some kind of workable idea.
As a suggestion for the show.


The Myth, you shouldnt hold a high gear, its not fuel efficient to cruise in top gear at lower speeds of around 30.

Or, What is more fuel efficient.... "cruising" in the highest gear the vehicle can hold, or hunting between gears.

The argument is...
As traffic speed changes, and you get the chance to speed up a little, some say hold the gear you are in and accelerate gently, others say downshift, accelerate, then change back up.

Maybe its just the car I am in.
I can hold 30 quite happily on even a gentle up slope, and accelerate even up to a 40 limit if the road changes to a 40 limit.
In 5th.

But some others say I should be down to 3rd to get from 30 to 40...

Maybe their car just hasnt got the gumpf, has no grunt, and they need to poke it a little.


I say if you have a micro engine, yeah, stir that pot of porridge, you probably need it.
But in a modest 1800 to 2ltr and above, I have the grunt to cruise at 2,000 rpm and accelerate, I need not disturb the gear box to do that.

Suggested test.... and what has been said already has reasonably been included in this.?..
Get a modest 2ltr or greater town cruiser with reasonable economy, not a gas guzzler.
Do a drive around town that will involve a little speed changing between 30 and 40 (or above) limits.
Do the test with [1st]... as little gear shifting as possible,
[2nd].... repeat with the change down to accelerate school of thought.

Then get a micro engine economy plus below 1300 cc thing, and repeat. Maybe even a 1,000 cc engine....
My guess will be that it wont hold 5th at 30, it wont accelerate, and you cant do the "Do not change down" test effectively anyway, but do try....
Then do the work at it of changing gear every time you need to change speed thing.

Comparisons should be the initial difference in MPG of the each vehicle due to change in driving style.
Then compare the two vehicles to see who is getting the better MPG and when.

My reasoning is based on my own vehicle and that of a friend, who's car I drive, mine has a larger engine, his is a 1300cc, smaller but capable, and he doesnt have 3 kids either.
In my car I can hold 5th quite easily.
In his, no way, it just wont tackle even the slightest of slopes, nor will it accelerate very well at 30 in 5th.

My viewpoint is it depends on the vehicle and the big talker who says his way is better should be quiet until he realizes that.

(The big talker that prompted this post drives a fizzy Golf (Rabbit in USA?..) with the smaller economy engine package...
He isnt getting that much better MPG than I am, but he does tend to be everywhere "yesterday" in his style of driving?...)

So how to alter this suggestion for an inclusion on the show ideas part?... any suggestions?...