[Closed] Fuel economy measurement - does it affect your driving style?

I'm always trying to keep that mpg figure as high as possible. Don't think my current car has ever been about 72 mph.

32 is piss poor by modern standards.
I only ever drove to the MPG when me and the missus had a game as to who could get the better average driving back from the alps (it helps avoid speeding tickets) I won with the downhill 150km stretch out of the alps where it was reading high 80's by the time we hit level ground.

If you can learn to relax and not "make progress" on every bit of road to arrive 3 minutes faster then you can change your ways. It's more a mindset of chilling out rather than going for it.

10mpg difference between really really trying amd just driving normally.

I try when I remember.

Nope. When I first got my car I used to marvel at how it could do 55mpg. Since then, I noticed the other week it was hovering at about 46/47mpg. I get about an extra day of commuting if I drive carefully but get about 2 weeks out of a tank anyway so I'm not really that fussed. I certainly don't let it affect how I drive. That all depends on a variety of other things as the OP states.

Last car (an M reg Micra) got ragged to within an inch of it's life along the short but fun country lanes commute. Current car, a 3 year old Jazz, shows an average MPG and I have a blissfully relaxed drive along the flat and uphill gently easing the throttle on and off and a banzai feet off the pedals downhill twisty run all in the name of enjoying the possible economy.

Virtually no difference in journey time (it's only 15 minutes anyway) and far greater economy. So yes, it has had an impact on my driving. Just enjoying a different challenge.

32mpg, well perhaps on a motorway cruise I might manage that. Then again I don't do a large number of miles so the actual cost of fuel isn't really a big deal for me.

My old 2.0 diesel used to avg about 35-40 mpg and I didnt try and improve the mpg as it appeared to make no odds.

My new 2.0 diesel averages about 60-65mpg. Has a nice display to tell you when you are recharging the battery, when the car is working efficiently etc. I'm currently trying to see if I can get to 70 mpg commuting.

Other days I drive fast and am amazed that I cant get it under 35 mpg !

My car has no MPG computer so I drive it like I stole it (joking obviously). It's a older TypeR - I care not for this fuel you speak of! I drove lots at the weekend started out with half a tank ended with a full tank and £85 of fuel receipts!

Depends how many miles you drive to a large extent, I would think.

I commute 400 miles per week so try to keep my mpg as high as possible.
The thing is, driving faster when it's rush hour rarely gets you anywhere faster, you just spend more time accelerating, braking or waiting at the next queue.

Before I started really trying to drive economically, 55mpg was about the most I would get over a tank and I'd be filling up around 500 miles.
Now, I can get into the 60's fuel economy. My last tank was actually the highest I've ever managed. I think it was a combination of the warm weather and luck with traffic, but I managed 613 miles at 68.8mpg. And that is from an 11yr old 1.9tdi with as near as dammit, 240k miles on the clock.
Psychologically, it is much nicer to visit the pumps less frequently, even if you can leave it an extra day.

If I need to get somewhere quicker, then I will drive quicker, but generally I try to keep an eye on economy.

Yes. The lower the numbers, the bigger the grin. 😈

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Yes. The lower the numbers, the bigger the grin

I certainly pay more attention to mpg than I used to. I suspect it's an age thing though. I don't seem to be in such a hurry these days.

It's not usually like that. It was just a particularly demonic drive. I've seen worse. It bottoms-out @11mpg as fiat (wrongly) believe it won't consume more. During the winter I can easily see 50, average B normally sits at about 35. Since I moved the fuel card to the oil-burner it's bizarrely got worse. Presumably as i drive it so infrequently now & have to get my "fix".

Part of the general info. on how my driving is -- don't drive to it, consciously, but happy to see the MPG in respectable territory. Return trip to Glasgow last week, incl. the dreadful A9 (dreadful as in driving standards) - shade under 40mpg, 2l petrol hatchback, is 18 years old though 🙂

These days I try and see if I can beat 50mpg on a tank full. It goes out of the window if I really need to get somewhere in a hurry but it's amazing what being careful can do to your mpg. Coasting down hills in neutral is probably the biggest single booster. Even though I don't have an instantaneous readout you can see the average click up within seconds.

I did manage 91.7 mpg over 33 miles last week on the M1. Pretty pleased with that.

Missus's car has this feature. She used to aim for the magic 60mpg barrier in it.

When I drive it, I can't see the display for some duff ergonomic reason, so generally no idea. Prob somewhere in the 40s for me.

Currently get about 52-56mpg with nothing other than brimming as a guide. On my old mans car I drive better as I like to play the MPG game 😛

Might see what Torque can throw up in the way of figures actually...

Coasting down hills in neutral is probably the biggest single booster

Hmm, for about the last 30 years, cars have been more economical on overrun in top-gear than in neutral as the ecu shuts off the fuel supply to the injectors* completely.

*carb-fed engines had this feature from about 1985.

I know that motorway runs drop my mpg in the landrover by about 3mpg per tank.

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My new motorbike should do 70-85mpg i.e. 3-4x better economy and is going to be used on most personal trips where Im not carting much around.

do a fair amount of commuting and for 20 mile Mway stints the difference between 55 and 75 is marginal....its not like i am in a rush to get to work and i am still getting paid

Good run at the traffic lights make more difference than hammering i IMHO

I also find driving in the inside lane at truck speeds less stressful than having to weave to avoid middle lane hoggers and those doing 90-100 mph.
No idea what my MPG is but about 450 miles from £40- apparently that is nearing 70 in a 1.4 diesel

Depends how many miles you drive to a large extent, I would think.

I commute 400 miles per week so try to keep my mpg as high as possible.
The thing is, driving faster when it's rush hour rarely gets you anywhere faster, you just spend more time accelerating, braking or waiting at the next queue...

... Psychologically, it is much nicer to visit the pumps less frequently, even if you can leave it an extra day.

If I need to get somewhere quicker, then I will drive quicker, but generally I try to keep an eye on economy.

As som said.

I have more time and less income, if I'm economical I can go to more places. It's that simple.

So, using the basis of a bunch of typical* STWers, it seems my devil-may-care attitude is costing me more than it ought!

I drive c20k miles pa, most of which is motorway commuting - hellish jams in the winter, and the last minute dash at fuel-inefficient speeds in the summer.

Car is a 2010 Mazda 3 2 litre Sport**. It's worthless (well, not quite) and owes me nothing, so I am loath to change it for something more efficient until it gives me other (repairs-related) reasons to switch cars.

Hmm. Maybe time to start an austerity drive.

*I'll let each of you reflect on whether that includes you....
**Ambitiously named, I feel, given it isn't that sporty.

If your slogging out the miles then the basics to cover are
Comfy Seat
Good Music
Good Fuel Economy

I was getting 50's in an N reg A4 tdi that had split climate control, nice seats and good music (when it worked) partly an efficient car helps and the other bit of not chasing the last minute of the journey. It makes very little difference.

We've just got a new Subaru XV. Not efficient by modern standards, 40-45mpg, and 48 if I go verrry gently on the rural roads. As its 2.0ltr and full time 4x4 I'm not too bothered. We don't do any commuting, so we aren't breaking the bank.

I'm sure that I can scrub a few miles off those figures, as the speed is more on the dashboard than the GPS, but that's the way for everyone isn't it?

I tend to find the distance to empty affects my driving more than the fuel economy.
Clocked up a big round trip over the weekend, and as I'd been driving during the day with a fair bit of traffic, so overtaking would've had limited effect on my overall journey, I took it quite easy. Halfway through the trip I realised that if I went easy the rest of the way I could probably make it home without filling up...

Getting the best MPG is pretty similar to caning it anyway, sort of. It's just as if you had absolutely terrible brakes and are afraid of high gears/high top speeds.

hot_fiat - Member
Coasting down hills in neutral is probably the biggest single booster
Hmm, for about the last 30 years, cars have been more economical on overrun in top-gear than in neutral as the ecu shuts off the fuel supply to the injectors* completely.

*carb-fed engines had this feature from about 1985.

It's an often quoted theory but it ignores a few basic facts.

While an engine may be using less fuel on the overun vs idle it will also be putting drag into the transmission which is slowing you down if the transmission is engaged.

What coasting does is reduce the engine revs to idle and allow gravity to be your energy source. It's often possible to maintain speed or even increase it over that on your entry and coast on for hundreds of metres at the bottom before needing to engage the gears again.

Trust me it makes a significant difference. Try it if you don't believe me.

I reckon electric cars could make very good use of it as a feature though it would depend how much energy they take to maintain an unloaded motor speed. Could be an interesting research project that. hmmmmmmmmmm

I reckon electric cars could make very good use of it as a feature though it would depend how much energy they take to maintain an unloaded motor speed. Could be an interesting research project that. hmmmmmmmmmm

The fuel economy comeptition cars do it by building up speed and then coasting for a long time with the equine turned off. Its the most efficent way to drive. Unfortunately it's not very safe and it doesn't work on the road.

I've found that coasting in gear into junctions is the biggest saver as you aren't using any fuel on the overrun and the braking affects are desireable. Coasting down hills in neutral may be efficient but pointless if you have to brake at any stage, you may well have used the engine braking on overrun and saved the fuel you would have used ideling.

So as a general rule of thumb it would be better to always coat in a high gear than in neutral as it's more beneficial in more situations.

gonefishin - Member
34mpg, well perhaps on a motorway cruise I might manage that. Then again I don't do a large number of miles so the actual cost of fuel isn't really a big deal for me.

Changed slightly above for me, do I alter my driving "style" I don't really have a style per se'. Do I drive slower or different to save fuel, No.

The fuel economy comeptition cars do it by building up speed and then coasting for a long time with the equine turned off. Its the most efficent way to drive. Unfortunately it's not very safe and it doesn't work on the road.

I've found that coasting in gear into junctions is the biggest saver as you aren't using any fuel on the overrun and the braking affects are desirable. Coasting down hills in neutral may be efficient but pointless if you have to brake at any stage, you may well have used the engine braking on overrun and saved the fuel you would have used idling.

So as a general rule of thumb it would be better to always coat in a high gear than in neutral as it's more beneficial in more situations.

In gear slowing down at junctions (or wherever) is really just good practice, the most efficient way of getting around will not use the brakes at all as you've obviously demonstrated.

Coasting down hills in neutral may be efficient but pointless if you have to brake at any stage

32mpg sounds good to me, currently averaging 27mpg over the last 4000 miles, previous car was averaging 18mpg over 20000 miles.

edited to add, driving to and from work I try to drive as efficiently as possible, outside that I forget the fuel economy

jfletch - Member

I've found that coasting in gear into junctions is the biggest saver as you aren't using any fuel on the overrun and the braking affects are desireable.

This is one of the things I do as a general attempt to improve observation/forward planning.
I approach a roundabout/junction and have to slow anyway. I might as well lift early, leave it in 6th and coast up to the roundabout. I sometimes use a very light brake pedal to let those behind know that I am slowing down, but depends on individual circumstance.
I also try to keep my speed up over roundabouts (not stupidly so), so I have to accelerate less on the other side. You can also brake a little harder on the approach if you see a car coming round so you can slot in behind it once it's past you, rather than have to stop as it is 'in your way' and then start from a stand still.

Lots of small tricks really, mainly down to observation that can help your overall fuel consumption.
It always amazes me the amount of people who will slot in behind me for a slip road exit that is coming up and then accelerate up the slip road to the roundabout/junction 150yds away, meaning they waste fuel and have to brake harder to gain fractions of a second.

Also maintaining a constant speed helps, rather than yo-yo-ing around a desired speed. I was behind a woman driving yesterday who appeared to be having quite an animated conversation with the bloke in the car with her. Every time she got more animated (arms waving around) she lost about 5mph, which she would then regain by accelerating back up to speed and then slowing down again.

God. That all sounds well boring!! I do enjoy giving it the beans but to be honest on my commute there is little point or enjoyment in doing so!!

jfletch - Member

I've found that coasting in gear into junctions is the biggest saver as you aren't using any fuel on the overrun and the braking affects are desireable.

I do this as well. Now we all know it's wrong and we would fail our tests again, but we just do it.. Does anyone do it on long hill descents?

Sui - Member

jfletch - Member

I've found that coasting in gear into junctions is the biggest saver as you aren't using any fuel on the overrun and the braking affects are desireable.

I do this as well. Now we all know it's wrong and we would fail our tests again, but we just do it.. Does anyone do it on long hill descents?

Coasting in gear is the recommended technique as far as I know. Are you mixing that up with coasting in neutral?
It used to be recommended that you changed down the gears as you slowed to use engine braking and so you are 'in the right gear', but I think the teaching now is more along the lines of slow using the brakes (which work a lot better than they used to), and then change gear when you get to your desired speed so you aren't doing two things at once.

Just out of interest, on my VW, when I'm effectively coasting down a hill or whatever the MPG rate goes to 199 I think then maxes out at "---"

does anyone know whether that "---" contributes towards the average or is ignored?

I've always wondered whether to get the average up (just for the hell of it) its better to keep the foot on the gas a little and keep it out of the 'max' zone??

I've always wondered whether to get the average up (just for the hell of it) its better to keep the foot on the gas a little and keep it out of the 'max' zone??

That --- just means you aren't using any fuel so the fuel economy can't be calculated as it's dividing by zero or you are beyon the capacity of the display, i.e. higher than 199.

Not using fuel is the best way to get the average up!

It maxes out because you're moving and using no fuel so you're doing infinity miles per gallon instantaneously. Annoyingly the engine and transmission drag is slowing you down far faster than you would be in neutral so while it's a good thing to do when coming to a halt as it's free braking, if you weren't coming to a stop, you'd probably have lost out.

agreed. so all those maxed out miles don't count towards upping the average??

Aww- that's not fair!

(I know in reality they do of course, but for playing the 'game' its a bummer)

http://www.popularmechanics.com/cars/alternative-fuel/news/coasting-in-neutral-fuel-economy

are your brakes dragging- in top gear i find it to have little effect on how far my car goes - while remaining safely in control of my vehicle should i need to make a sudden adjustment to my speed or my direction.

oh and wether i go at 65-70 or 82 on the french peage i return between 39-42mpg in my non turboed diesel.

trail_rat - Member
> http://www.popularmechanics.com/cars/alternative-fuel/news/coasting-in-neutral-fuel-economy

are your brakes dragging- in top gear i find it to have little effect on how far my car goes - while remaining safely in control of my vehicle should i need to make a sudden adjustment to my speed or my direction.

oh and wether i go at 65-70 or 82 on the french peage i return between 39-42mpg in my non turboed diesel.

TR - that's a perfect example of why you shouldn't believe everything you read on the internet. Read the comments below and you'll begin to understand that the guy is compare apples and pears. He's talking about coasting to a stop in gear off throttle vs out of gear at idle and that's a no brainer. What we're all talking about it knocking it out of gear downhill and coasting as far as you can within reasonable speed limits.

Re the control thing the only thing I'm missing is the ability to speed up and if I need to do that significantly I'll have to change down from 6th anyway so it's reaction time neutral. The brakes and steering still work as they would normally so safety is in no way compromised.

so provide some evidence to the contrary then ? other than your opinion. that is not my basis for my opinion - it was just the first hit on google.

The "199mpg" reading is your ecu shutting the injectors off. It's all added to the average.

It takes about 720w to cold crank an average engine at 1500rpm (12v X 60a). An average family car's brakes are capable of producing about 350kw (yes, about 500hp). Engine braking is pretty pointless.

hot_fiat, your value for brake power must be a max value? You probably brake normally with 10% of that or even less?

What does 'engine braking is pointless' mean? In 6th gear, yeah maybe. But change from 6th to 4th in my car at 70 and take your foot of the throttle and you really notice the engine braking.
Find a steep hill and drive down it with your foot on the clutch. Now do it again with the car in 3rd gear....any difference?

Given the frequency I have to check the speedo in this radared age the instant fuel consumption has become my favourite option for the other readout. It tells me fascinating things like the optimum gear for crawling along at the speed limit. Third for 30kmh limits, Fourth for 50kmh limits and fifth above 60kmh. 75-85kmh in fifth is the speed that returns the lowest fuel consumption with a steady increase thereafter (so fifty really is thrifty). Up mountain passes a light throttle opening with the engine spinning at peak torque yields the best results.

Winter tyres really do use more fuel that economy tyres at the same speed on the same road. It's worth changing down rather than rolling up to junctions in a high gear as it cuts off the fuel. Using a route nationale uses less fuel than the autoroute even if the nationale goes through towns. 5.7l/100km on petrol over the last year according to the average economy readout.

On the downside it's just another distraction.

Coasting in gear.. hmm.. it uses no fuel, but it slows you down a little quickly sometimes. I reckon when you are approaching a roundabout or something you can lift off and give it just a tiny bit of pedal (rather than none), you slow down very very slowly but your mpg goes through the roof the whole time. Of course not suitable for busy traffic where being 'normal' and flowing with everyone else takes precedent.

I do drive for fuel economy, of course - but without being an idiot about it. I put my cruise on 70 on the motorway and relax. On windy roads I concentrate on being as smooth as possible, keeping my momentum as much as I can and putting in bursts of throttle at the right times, coasting at others. I also use cruise whenever possible in 40s and 30s to keep speed consistent. I've noticed that if you ease down on the pedal so gently that you don't notice any acceleration, the mpg still goes through the floor, so cruise limits these constant variations.

I got 62mpg from Cardiff to Farnborough the other day, in my auto pre-bluemotion Passat.

Incidentally, before I got the Prius I'd drive at 80 everywhere and not hang around on normal roads. Only when I got the graphical readout on the Prius did I see how much effect it had on my averages, and because I bought the car for economy (why else) I started trying to keep it up as much as possible. I do wonder what my Seat would have done had I driven it knowing what I now know.

Winter tyres really do use more fuel that economy tyres at the same speed on the same road.

Depends on the tyres - Nokian WR G2 were a huge improvement in MPG over the Dunlop Sports - about 10%.

Given up worrying about it - however I drive (mostly dual carriageway) it only makes about 1.5p per mile difference.

30mpg average on a tankful is but a dream to me.

Incidentally, I got 62mpg coming down to Surrey the other day; I did 82mph on the way home and got 54mpg.

I did a little experiment a while back. Spent an entire two weeks driving as gently as possible. Real granny stuff. Coasting every hill in neutral, as far as I possibly could. It was difficult. The urge to hit the accelerator, just squeeze it a bit and start moving a bit faster was strong. And once I'd rinsed a tank of petrol, I discovered it hadn't really made any difference at all.

Don't have a fancy pants computer, so not a massively accurate experiment (I know how much I get to tank...), but it seems either:

a). I don't have a car that responds well to economical driving.
b). It's all bo**ocks.
c). I'm a very economical driver already.

I discovered it hadn't really made any difference at all

You did it wrong then. Driving economically isn't necessarily about driving slowly. Accelerating slowly for example is worse than accelerating moderately and holding speed.

Lowering your cruising speed does make a big difference on motorways though.

butcher - Member
And once I'd rinsed a tank of petrol, I discovered it hadn't really made any difference at all.

Where as in mine (2.0 DCi) it can make up to 100m difference over a tank of fuel driving conservatively vs normally.

conservatively means:-
70-74 indicated on cruise control on motorways (depends on traffic conditions and how much of a hurry I am in)
60mph on A roads
40-42 indicated in a 40
30-32 indicated in a 30
driving to conditions everywhere else
Coast out of gear down as many hills as possible and aim to be back in gear on throttle before I get bored or something catches me up
Use as light a throttle as possible to maintain those speeds and as few revs as I can get away with (helps it's a torquey 2 litre turbo diesel)
That's not to say I don't make progress or overtake when the opportunity arises. I dare say I could get another 5mpg consistently if I were more patient.

Oh and Aircon - I haven't done a major comparison between on or off as I don't do any regular journeys to measure it on but it certainly feels like it's a big drain.

I never turn my A/C off, I let it manage itself. If there's any difference (on either car) between A/C on and off, it's lost in the variation of different journey types.

I don't do the same trip all the time though so I don't have good reliable data to compare small changes.

molgrips - Member
I never turn my A/C off, I let it manage itself. If there's any difference (on either car) between A/C on and off, it's lost in the variation of different journey types.

I've tried a week here and there with my climate control set to econ which basically turns the air-con bit off and there is no appreciable difference. Like you say, I suspect any improvement is lost in the week to week variation from things like traffic, short trips into town etc.

I think on smaller engines it makes a difference. My Wife's Ka had aircon and it was noticeably more sluggish with it on. But that was a 1.3 8v with about 60hp.

Depends on the tech I think. I went out with a girl who had a Hyundai Accent, about 2000 or so. It was American spec so had a pokey de-tuned 1.6l engine with a crap old fashioned auto box and presumably a massive old-tech A/C compressor. In all the older cars I've read Haynes manuals for there's a switch to disable the AC when you floor it, but this didn't have it. If you were attempting to accelerate to motorway speeds, you could hit the A/C button and feel a proper kick of acceleration.

Most A/C clutches are disengaged by the ecu upon peak throttle demand. In the abarth you can hear the high pressure side re-pressurising following bouts of heavy footedness.

@stumpy - you'd be surprised how hard brakes actually work. Yes 500hp is peak. Though I wouldn't have thought 80-100hp was an unreasonable braking power for normal deceleration, even around town. (you decelerate a damned site quicker than most cars accelerate).

Peak power from engine braking really does max out at a couple of KW. Its fine for holding your speed down a hill, if you're a mentalist & like to unsettle a car before a corner, or if you think that's how racing drivers drive (they don't*); but for actual slowing down brakes win.

*in fact one of the many unsung technologies that's come out of racing is MSR which actively works with the electronic throttle to reduce the effects of [s]botched downshifts[/s] engine braking to ensure smooth transition into the bend. In a passenger car this is used to assist ABS in preventing wheel lock-up. In reality it's all the same system doing the thinking, just Bosch like acronyms.

Yeah, doing a quick fag packet calculation, braking power is quite high!

I get a car (1500kg) braking from 70mph to zero in 15secs needs the brakes to work at a constant rate of 48kW, which is about 64hp.
And I suspect most people coming off a motorway to a roundabout or junction don't give themselves 15s to stop.

(Using: KE at 70/time taken to stop to get the power required and then dividing that by 745W (1hp).)
A lot of assumptions in there - it wouldn't be linear for a start.

Always an interesting one. I drive a 2 litre diesel BMW and average 43mpg (about 550 miles to £80) however on a long run I can extend that more towards 47mpg (closer to 650 miles) however I find that my driving style changed due to my job and I guess, maturing. Gone are the days of being slightly aggressive with the car and now being smoother. I havent noticed a dramatic increase however I live in a city, commute out through city roads to dual carriageways to B roads.

I maintain if I get a job in the city I will probably commute by walking or cycling however I would look to sell my heavy and cumbersome diesel and buy a more modern petrol as I will be doing 10 minute trips to the shops and back more often.

Maybe Im wrong but for those short journeys a lighter petrol car will probably warm up quicker and handle the stop start of city life better and more efficiently than a diesel over a ten minute period. This is based upon the fact my car is 10 years old and recently I had a Skoda brand new 1.2 TFSI petrol for a few weeks that was averaging about the same MPG as my diesel when comparing fuel price difference.