fuel saving tips please

[Mr Ree]

Not over cynical, but you overestimate the gov's tax-collecting averice. The traffic lights are simply there to delay you and to discourage you from using your car. Hope that helps

Good point, so let's settle on both of our cynicalsitic thoughts.

[pullover]

My 1.8TSI (59-reg FL) will do 45-50mpg on 10 mile mostly motorway commute. But them I'm not usually in any rush to get to work. I have found with this TSI engine mpg really is driving-style dependant. It'll do 30mpg if I race to work.

[Metblackrat]

Also, be careful trying to use coasting to stretch yer miles per gallon - I believe it's illegal as you are required by law to be in control of the vehicle at all times. "Coasting" means that the engine is disengaged from the road wheels and the car will become unwieldy and difficult to nigh on impossible to keep under control at speed.

You have just described how some auto boxes work.

[mattrixdesign2]

I have saved a small fortune on fuel, simply by breaking my leg, had free lifts from the wife and colleagues since before Christmas... But it gets annoying after a while so think twice before committing yourself.

[keith3289]

Discovered almost by accident last week,(as if I didn't already know) that stop start driving due to the ever increasing number of ruddy traffic lights is a MASSIVE fuel user.

Yes, I have a 25 mile commute, mixture of urban, rural and dual carriageway and normally get 35mpg if I avoid the morning peak. Leave 45 mins earlier and I'm down to 30mpg, and it takes 30 mins longer!

[Mr Ree]

Yes, I have a 25 mile commute, mixture of urban, rural and dual carriageway and normally get 35mpg if I avoid the morning peak. Leave 45 mins earlier and I'm down to 30mpg, and it takes 30 mins longer!

Never ceases to amaze me just how many people out there haven''t got the foggiest how many mpg their car does, and more staggeringly, don't even seem to care!!

Don't even bother engaging in conversations on how to obtain better fuel consumption.

"Oh, I just fill it up and carry on until the orange light comes on" is the usual reply. :no:

Recession? What recession it seems?

[Kiwibacon]

Pulse and Glide works because your engine is more efficient at higher load.

So you give it higher load for acceleration, then coast in-between. Because you are burning the majority of the fuel in a more efficient operating point, the total fuel consumption drops.

But there are two things to watch.

1. On a petrol don't pulse into "enrichment", you need to find the point of highest load before the computer starts dumping fuel in. If you have readout (maybe some OBD2 plug-ins will tell you) of A/F ratio then you'll spot the A/F ratio dropping as it hits enrichment.

2. It is only worth doing on a petrol. Because of the throttle plate on a petrol and the large pumping losses at part throttle, there is a bigger difference between best and worst operating points. On a diesel the whole map is a lot more even, to the point where pulse and glide for the majority isn't worth the hassle.

On a diesel it's smooth driving and high gears that work in general. Some engines are a bit more picky than others.

In gear with no throttle is engine braking. Good if you need to hold speed (i.e. downhill) or slow down, but not good for fuel economy.

[ambrosevonpose]

most fuel is used during the initial acceleration from lights,junctions etc until you get into top gear

I did an experiment in my car on my local part of the motorway - Did a 10 mile journey doing 55 mph and i got around 57 mpg - then i did the same journey doing a lot more if you know what i mean and I got 56 mpg. The saving didn.t seem to justify the boring journey and extra time taken

[Jockdooshbag]

most fuel is used during the initial acceleration from lights,junctions etc until you get into top gear

I did an experiment in my car on my local part of the motorway - Did a 10 mile journey doing 55 mph and i got around 57 mpg - then i did the same journey doing a lot more if you know what i mean and I got 56 mpg. The saving didn.t seem to justify the boring journey and extra time taken

By a llot more you probably mean 80mph seeing as you wouldnt say. I dont believe a petrol VRS got 56mpg doing 80mph unless it was all down hill. I know accurately what my old Audi S3 got at 80mph and the same goes for my Golf 170PD DSG, my BMW 320D and my current CR TDI DSG and non of them get or got 56mpg at 80mph. The closest was the beemer that would average just over 50mpg at 80mph indicated. The Golf would be high 40's say about 48mpg. I have only tried my CR TDI over shorter distances so far but ive yet to see above 50mpg at 80mph average. My old Audi S3 with the 1.8 Turbo engine got about 42mpg at indicated 80mph and this was over many very long journeys including to the alps.

Unless you used a different car from the one mentioned in your profile then i simply dont believe it. Sorry.

Just re-read your post and in fairness yours may be a CR VRS so apologies if i have wrongly assumed its a petrol. I still dont believe 56mpg at 80mph is possible though even for a TDI VRS.

Edited 5 February, 2013 by Jockdooshbag

[stever750]

Pulse and Glide works because your engine is more efficient at higher load.

So you give it higher load for acceleration, then coast in-between. Because you are burning the majority of the fuel in a more efficient operating point, the total fuel consumption drops.

But there are two things to watch.

1. On a petrol don't pulse into "enrichment", you need to find the point of highest load before the computer starts dumping fuel in. If you have readout (maybe some OBD2 plug-ins will tell you) of A/F ratio then you'll spot the A/F ratio dropping as it hits enrichment.

2. It is only worth doing on a petrol. Because of the throttle plate on a petrol and the large pumping losses at part throttle, there is a bigger difference between best and worst operating points. On a diesel the whole map is a lot more even, to the point where pulse and glide for the majority isn't worth the hassle.

On a diesel it's smooth driving and high gears that work in general. Some engines are a bit more picky than others.

In gear with no throttle is engine braking. Good if you need to hold speed (i.e. downhill) or slow down, but not good for fuel economy.

So why not simply keep the engine speed at its most efficient point? What is the benefit of drifting out of that band and then accelerating back into it? Or have I misunderstood it, and you pulse the throttle to keep engine speed constant over inclines and down hills? Except that would simply be maintaining a constant speed in a fixed gear.

I'm still struggling to see how it works.

Sent from my GT-I9300 using Tapatalk 2

[Kiwibacon]

Steve, because engines are grossly over-sized to provide acceleration. Trying to run for example a 1.8tsi engine at it's most efficient point would require much higher gearing and driving aroudn 180km/h.

And then, while it's efficient, you're burning a huge amount of fuel because you're running at a high load all the time.

Diesel engines do run closer to their most efficient point already. Which is another reason why pulse and glide techniques aren't worth it on diesels.

Pulse and glide is simple.

Accelerate with the engine in a most efficient spot and glide using as little fuel as possible in between. How much speed variation you get depends on how much work you want to put in. You can accelerate/coast in a 5km/h band if you want. But it's hard work.

A naturally occuring version of pulse and glide happens on drives in rolling hills where braking isn't needed on the downhills. There is one particular trip which in my last petrol car would return about 10% better fuel economy than the usual. Because I was driving up the hills at a higher load (more efficient engine operating point) and coasting down the other side using minimal fuel. I did this trip several times in that car and got the same result.

[Gazman]

If you have climate then switch it to econ, noticed I got a rise between 1 to 2 mpg after I did that, be sure however to switch the temp to low once a week for 10 mins just to stir the coolant and keep it from deteriating....

[Gazman]

Took mine out for a long run today and did about 140 miles of motorway and A roads, driving like a vicar I could not better 37.8 mpg, my tyres are all at 32 psi and my air filters new, admittedly the temp was at max 4c, will try running the car on vmax or similar higher octane fuel and see the results....

[Gazman]

Took mine out for a long run today and did about 140 miles of motorway and A roads, driving like a vicar I could not better 37.8 mpg, my tyres are all at 32 psi and my air filters new, admittedly the temp was at max 4c, will try running the car on vmax or similar higher octane fuel and see the results....

[booke23]

You'd probably better that figure by 10%, doing the same trip on a nice summers day.

[Gazman]

You'd probably better that figure by 10%, doing the same trip on a nice summers day.

What I figure as well, just hoped I would have seen 40, been happy enough with that. More likely gonna drive it to Heidelberg, Germany in April and am banking on 3 tanks there and back, it's about 480 miles each way and usually 6 hours, not including the boat to dunqurque..

[booke23]

Once you get onto those autobahns you can kiss goodbye to good fuel economy!

[stever750]

Hmm. An engine will be at its optimum efficiency at a fixed speed (rpm). Surely just drive at that? The instant fuel consumption display is your friend here. One of the big benefits of CVT is that the engine sits at its most efficient speed and therefore acceleration and economy.

My car is at its best when I use cruise control, by 3-4 Mpg so far.

Sent from my GT-I9300 using Tapatalk 2

[Gazman]

Once you get onto those autobahns you can kiss goodbye to good fuel economy!

Well yeah maybe for an hour or so of fun, but I'll have the Mrs with me and she makes a whining noise at +90 :-(((

[Gazman]

Hmm. An engine will be at its optimum efficiency at a fixed speed (rpm). Surely just drive at that? The instant fuel consumption display is your friend here. One of the big benefits of CVT is that the engine sits at its most efficient speed and therefore acceleration and economy.

My car is at its best when I use cruise control, by 3-4 Mpg so far.

Sent from my GT-I9300 using Tapatalk 2

I still have to find mine, certainly was'nt at the 2000-2500 rpm I was at most of today, I used cruise for the times I was on the motorway but that was no more than 50 miles, rest was small a roads and around 50mph...

[MarkEll]

Took my Blackline out for a spin today (50 mile trip) averaged 61mpg! Never expected that at all. Didn't boot it but really go to easy

[Gazman]

Took my Blackline out for a spin today (50 mile trip) averaged 61mpg! Never expected that at all. Didn't boot it but really go to easy

Haha, go on then rub it in..I missed my old diesel car but the mileage I do and additional purchase price did'nt really make it worthwhile, would'nt rule out going back to one though if my circumstances change

....

[booke23]

Well yeah maybe for an hour or so of fun, but I'll have the Mrs with me and she makes a whining noise at +90 :-(((

I get that whining noise too!

[Kiwibacon]

Steve, to drive a TSI at it's max efficiency point, you'll be doing probably 180km/h.

This is of course impractical and illegal. So you can pulse accelerate using points near that max efficiency and glide in between. This gives better fuel economy.

Petrols at part load are terribly inefficient. They strangle themselves with their own throttle plates.

[littleade]

Took my Blackline out for a spin today (50 mile trip) averaged 61mpg! Never expected that at all. Didn't boot it but really go to easy

That seems about right- I get low 50's on a run, but that's doing the legal max all the time +10% ish where posible & safe to do so and some 'spirited' acceleration. I'm averaging 49 at the mo. I find it difficult driving like miss daisy in a vRS- I used to in my 1.4TSI but the BL returns better MPG figures (TSI averaged 44)even when driven significantly faster- I could do with driving her like miss daisy at the same speeds I did with the TSI as an experiment to get a true comparison.