Driving economically, which gear and RPM

[obi_waynne]

Ok then, so lets debate your gear changing techniques and selections when driving economically.

Here are the schools of thought on this...

The brain says keep the RPM as low as possible and always choose the next gear up if the engine can pull without labouring.

Logic says economy happens at the peak part of the RPM torque range and you need to keep the engine in that sweet spot.

Surely though 1800rpm would use more fuel than 1000rpm?

What can you add to this debate and deliberations?

 

[Aerial Andy944]

Low rpm for me. Accelerate to speed needed then change to sixth to cruise. I do coast a lot with no acceleration applied but still in gear as was told this way of coasting used no fuel at all. My mpg is normally around 52mpg in mixed driving. Torque of the engine and vehicle weight would matter also wouldn't it? Driving father in law CMax tdi 140 in same style and I couldn't get above 48mpg even on the motorway!

 

[davalav]

Highest gear I can without any hiccups. my GF's new Beetle I averaged roughly 48mpg. Not bad for a compound charged 1.4! Her driving style is shocking, she barely manages 28mpg!!!!!

 

[Aerial Andy944]

Her driving style is shocking, she barely manages 28mpg!!!!!

Same! Mrs Parrys driving leaves something to be desired.
So far damaged rear bumper and exhaust mounts, how!(we have parking sensors for goodness sake!). Damaged rear wing, curbed wheels and 3 complete wing mirrors smashed off! Love you Mrs P.

 

[obi_waynne]

My wife always gets better economy than me.

My take on this is that you need the right gear for the job. The highest gear and low revs works only for cruising on the level. When you hit a hill or need to accelerate you need to keep the engine at the start of it's power band for most efficient use of your fuel.

If you can't do that then just accelerate briskly, not stupidly hard but briskly to your cruising speed and maintain that. You'll be surprised how much fuel is wasted asking the engine to pull the car in too low a gear.

 

[T9 man]

Same! Mrs Parrys driving leaves something to be desired.
So far damaged rear bumper and exhaust mounts, how!(we have parking sensors for goodness sake!). Damaged rear wing, curbed wheels and 3 complete wing mirrors smashed off! Love you Mrs P.

Oh bless her, does your young lady have shares in Euro Car Parts by any chance Andy?
Her indoors is a bit of a Frank Spencer in a skirt as well, that's why I had the rear view camera fitted to the Beast, somehow the rear parking sensors were just too confusing for her

I should have traded her in ages ago for a younger fitter model, but I have invested 10 years plus training her up and getting her use to my funny little ways

 

[T9 man]

My wife always gets better economy than me.

Now I have no idea how her indoors gets on with regards to fuel economy in the Beast and quite frankly I don't care!
But in her own Ford Focus convertible, I swear if the town run is quoted by Ford as 35 mpg then she will make it her mission to get 36 mpg

 

[Teo]

Ok then, so lets debate your gear changing techniques and selections when driving economically.

Here are the schools of thought on this...

The brain says keep the RPM as low as possible and always choose the next gear up if the engine can pull without labouring.

Logic says economy happens at the peak part of the RPM torque range and you need to keep the engine in that sweet spot.

Surely though 1800rpm would use more fuel than 1000rpm?

What can you add to this debate and deliberations?

I always do my best to keep a low of 6500 rpm for every shift, because at 6600 rpm my fuel consumption suffers and my supercharger whines too loudly!!

 

[SLEEPER]

easiest way to get lerss worse on the caldina is to keep the boost guaje under zero.

 

[jarrus]

Impossible for me to get under 0 boost on my car, I get 10psi on a cruise...diesel though mind,
Last month I got an average of 35mpg out my green turd... mainly because I drove it like I stole it,
Something I've noticed though since owning it is that even though the 205 is a much lighter car than the 306, general driving my 205 and 306 return about the same mpg... why? has to be the engine, one is a 1.8 td the other is a 1.9 td, they are basically the same engine... the only difference is the 3mm in the bores (crank, rods, head, cams turbo etc etc is all the same) but for some reason the 1.8 is completely gutless off the turbo were the 1.9 has some guts and there for I change gear earlier and use less right foot....
weird eh?

But you do also have to consider the car you're driving, a guy at work has recently bought a mustang (GT 2000 year with the 4.6 modular v8 making around 260hp) and he told me he gets 18 mpg driving 7 miles to work and 7 miles back which aint bad really, but what I don't get is when people as him how much fuel hes using.... his response is "do you think Im worried about fuel economy if I've bought a v8 mustang" ..lol
also to consider is uneconomical economical cars as I like to call them....
fiat 500 twin air.... that thing get no where near what fiat quotes.... 40mpg if youre lucky (my sister had one for 6 months and couldn't get more than that, considering fiat claim 60 something around town)

just drive properly and enjoy your car....

 

[HDi fun]

There are no hard and fast rules really. There's nothing to be gained from grannying an engine ie. using a gear that is too high. It won't breathe properly for a start! Plus you'll load up the crank bearings and small end bearings massively at a time when your oil pump is not delivering full pressure which makes things worse still. I think staying around the peak torque point during acceleration and getting on with the job, ie. get up to your road speed swiftly and then select a higher gear for cruising is probably the way I'd approach it.

 

[MaTroy23]

In a petrol car keeping your RPM between 2000 and 3000 is considered the economical range. If you can drive between 2000 and 2500 and change gear before 3000 your driving economically. This is why in most small cars 55 mph is considered the economical speed on motorways because your be at about 2800 rpm in a little 1.2 litre car.

Also driving habit makes a difference, harsh braking as well as harsh acceleration plays a part as well as smooth gear changing. you can jump gears as well 2nd to 4th or 3rd to 5th as acceleration uses a lot of fuel, this means less time spent accelerating through the gears.

Another factor is not changing down and using the engine revs to slow the car, pull up to the lights then change gear. And dont ride the clutch, use your handbrake!

Having roof bars and stupid bobbley things on your areal for example make a surprisingly big difference.

 

[obi_waynne]

Having roof bars and stupid bobbley things on your areal for example make a surprisingly big difference.

I've never understood why people fit those things to aerials!

 

[MaTroy23]

I've never understood why people fit those things to aerials!

Well not only do they look silly they cost you more in fuel lol
Also driving with your widows closed is more fuel economical and driving with your arm out the window causes even more drag lol

 

[MaTroy23]

Lol on that note, My Volvo C70 with the roof down definitely does not get as good MPG as it does with the roof up

 

[HDi fun]

Aerodynamic drag does play a bigger part as speed increases. It's commonly said that, at motorway speeds, air-conditioning uses less fuel than having windows open.

According the the Daily Mail - that font of all knowledge - this is actually wrong. The DM states that air conditioning will always use more fuel than open windows.

I agree with the DM totally, it's absolutely correct. This time anyway.

What the DM is failing to tell us is how we are actually supposed to keep cool.

I mean, my lawnmower uses more electricity than my electric razor. Of course it does. But I don't try and cut my lawn with my razor do I? Nor do I shave with a Flymo !!

 

[MaTroy23]

I think you have to draw a line somewhere. Using your car stereo uses fuel, using your lights uses fuel. and so on. as long as we understand that we can decide where we want to save and where we don't.

Personally id rather have the air conditioning on because the cabin filter dosent let the pollen in on hight pollen count days and stops the inside of the car smelling like the m25. also anything I have in the car dosent get blown around. So I drive smoother and find other places to save fuel. I am still driving more fuel economically than if I don't care at all.

But If you drive with the windows open and you use a little less fuel than me but, say, you drive at 80 wile I'm driving at 60 - 70 then your still doing your bit.

Just before I got rid of my Seat Arosa 1.0 I did a test where I never went over 55mph never put the stereo on or the heater, had the windows up, only put the lights on when it started getting dark and all the other things. I went from averaging 270 miles to a tank of fuel to 330 miles to a tank. I was surprised how much difference it made. but god was I board with no music, hot with no heater blowing cold air. and frustrated at grandmas overtaking me lol

 

[Yugguy]

IMO it is best to get up to cruising speed smartly and then stick at an rpm where you are using your torque rather than your revs.

 

[Aerial Andy944]

I think you're finding the 63hp engine is woefully underpowered to accelerate the car mass so you're pressing the accelerator more which is using the fuel more quickly. The turbo is helping your fuel consumption not harming it.

 

[MaTroy23]

Whos car is 63hp? Sorry im confused by this message

 

[Aerial Andy944]

I think you're finding the 63hp engine is woefully underpowered to accelerate the car mass so you're pressing the accelerator more which is using the fuel more quickly. The turbo is helping your fuel consumption not harming it.

Whos car is 63hp? Sorry im confused by this message

The thread has been edited by looks of it and some of the posts have disappeared. Someone thought removing the turbo from his 3cyl engine would improve his poor fuel economy

 

[HDi fun]

IMO it is best to get up to cruising speed smartly and then stick at an rpm where you are using your torque rather than your revs.

That makes perfect sense. When the oldies describe getting into top gear (whether 4th, 5th, 6th, or even 3rd if we wind back to the 1940s) as soon as possible it's meant to mean use the engine's optimal power range to gain speed rapidly.

Some people (including both my parents) seem to think it means changing up at the lowest revs when the car will just avoid stalling in the next gear. My Dad changes up at 1500rpm. He's into fifth gear well before 35mph. In his opinion it's good for the engine.

This is an extreme example of stupidity.

He manages 34mpg from a 12 plate 1.4 Corsa (petrol). It has had significant emissions problems getting through its first MoT. But he thinks the problem is caused by my mother who changes up at (shock horror) 2000rpm. He thinks that she is hurting the engine by revving it to 2000rpm.

 

[MaTroy23]

The thread has been edited by looks of it and some of the posts have disappeared. Someone thought removing the turbo from his 3cyl engine would improve his poor fuel economy

lol that would be hilarious to see.

 

[MaTroy23]

@HDi fun, I agree

 

[obi_waynne]

The logs don't show any deletions from this thread! There was another thread about removing a turbo to make a car more economical though.

 

[Aerial Andy944]

It's definitely gone Waynne. The guy had posted in this thread and introductions section

 

[T9 man]

^^ Not guilty your honour!

 

[Aerial Andy944]

Well back on topic, just put some BG244 cleaner through and my mpg is running at around 55mpg. Seems a good clean through of the fuel system works wonders. Still accelerating briskly to speed then straight into appropriate cruising gear, usually 5th or 6th.

 

[HDi fun]

Ironically it's diesels, which are generally bought with a view to fuel economy, are generally best maintained in optimal running order by driving them 'uneconomically' .. ..