This morning on my regular 24 mile commute to Buxton I got 48 mpg instead of the normal 44mpg. The only thing I did differently was I kept it in 5th gear up the first long ascent out of Chesterfield.

Pulls fine in 6th up that hill (A619) but would revving slightly higher in 5th really give better mileage? I usually get 53 ish mpg on the return journey as there seems to be so much more "coasting" involved.

Interesting..... I always get into as high a gear as I can as quickly as possible, but maybe that is not the right thing to do.

It's probably that in that gear and at that speed the engine r.p.m is at peak torque and hence it's running at it's most efficient.

Sometimes the engine is labouring more when you go to a higher gear to early, and you actually end up using more throttle then when in the lower gear...

More throttle means the engine may be using more fuel, it's not as drastic a difference with modern computer controlled engines as it used to be, but the engine is working harder than it should do if you change up too early...

Yup, I've found similar with my PD170. I used to drive a PD105 which was more efficient under load at lower revs in high gears (8 valve engine vs 16). Had to adapt to settling for a gear lower sometimes in the PD170.

... I usually get 53 ish mpg on the return journey as there seems to be so much more "coasting" involved.

This phenomenon (did I pronounce that correctly?) is something I've only caught on to recently.

My commute to/from work in my 1.4TSI is less than yours, but the difference between to and from (albeit according to the dashboard readout) is typically up to 5mpg. Apart from one obvious but short hill section on a motorway, you would be REALLY hard pushed, without seeing the contours on a map, to guess which way was ultimately uphill or downhill.

Point being, you need to measure economy brim to brim over a reasonable time period and distance, rather than take a snapshot of a one way (no matter how short or long) journey.

If the engine is cold for the first climb then it's usually better for economy to let it run to 1500-2000 rpm. Once it's warm, the highest gear it can pull without labouring will usually be the best for economy. You can get amazing mpg figures from runs that start downhill too as the engine can warm without being loaded too much.

If the engine is cold for the first climb then it's usually better for economy to let it run to 1500-2000 rpm. Once it's warm, the highest gear it can pull without labouring will usually be the best for economy. You can get amazing mpg figures from runs that start downhill too as the engine can warm without being loaded too much.

Except the next morning when you need to return home!

This morning on my regular 24 mile commute to Buxton I got 48 mpg instead of the normal 44mpg. The only thing I did differently was I kept it in 5th gear up the first long ascent out of Chesterfield.

Pulls fine in 6th up that hill (A619) but would revving slightly higher in 5th really give better mileage? I usually get 53 ish mpg on the return journey as there seems to be so much more "coasting" involved.

Out of curiosity have they sorted out the horrendous pot holes on that stretch yet? Last time I went down there it was horrible!

This morning on my regular 24 mile commute to Buxton I got 48 mpg instead of the normal 44mpg. The only thing I did differently was I kept it in 5th gear up the first long ascent out of Chesterfield.

Pulls fine in 6th up that hill (A619) but would revving slightly higher in 5th really give better mileage? I usually get 53 ish mpg on the return journey as there seems to be so much more "coasting" involved.

It is not just what you do going up the hill that counts but what you do going down the other side. Going up the hill or anywhere under load it seems best to keep the engine just below the point where maximum torque starts, which I think is about 1700-1800 on most CR and TSI engines. Down the other side of the hill free wheel. Much disagreement on this but I am convinced by carrying out by Thermo-dynamic system analysis, as long as you do not have to break much, it is worth doing. Also on gentle acceleration jump a gear ie go 1,3,5 or 2,4,6 and of course all the other stuff, only carry stuff you need, good predictive driving. We get 43 MPG often out of our TSI VRS, use to get near 60 mpg on a run in my 130 hp PD A4. Thought about a thread for the maximum range shown of the fuel computer, got to 1000 miles on the A4, have not manged 500 on the VRS yet but will no doubt. But do max it sometimes.

Point being, you need to measure economy brim to brim over a reasonable time period and distance, rather than take a snapshot of a one way (no matter how short or long) journey.

:yes:

There are so many variables that you can't judge it on a single day - it could be down to something totally unrelated such as the wind being in a different direction that day.

Yup, I've found similar with my PD170. I used to drive a PD105 which was more efficient under load at lower revs in high gears (8 valve engine vs 16). Had to adapt to settling for a gear lower sometimes in the PD170.

Exactly the same for me too, moved from a 90bhp (non PD) TDI to a 140bhp, had to train myself to change gear more often.

We get 43 MPG often out of our TSI VRS,

Bloody hell! low 30's as a rule 35 on a run.

It is not just what you do going up the hill that counts but what you do going down the other side. Going up the hill or anywhere under load it seems best to keep the engine just below the point where maximum torque starts, which I think is about 1700-1800 on most CR and TSI engines. Down the other side of the hill free wheel. Much disagreement on this but I am convinced by carrying out by Thermo-dynamic system analysis, as long as you do not have to break much, it is worth doing. Also on gentle acceleration jump a gear ie go 1,3,5 or 2,4,6 and of course all the other stuff, only carry stuff you need, good predictive driving. We get 43 MPG often out of our TSI VRS, use to get near 60 mpg on a run in my 130 hp PD A4. Thought about a thread for the maximum range shown of the fuel computer, got to 1000 miles on the A4, have not manged 500 on the VRS yet but will no doubt. But do max it sometimes.

WHOAAAAHHHHH!

"Down the other side of the hill free wheel."

I was told that this is not indictable, but nonetheless illegal and not good practice on safety grounds - can anyone enlighten?

WHOAAAAHHHHH!

"Down the other side of the hill free wheel."

I was told that this is not indictable, but nonetheless illegal and not good practice on safety grounds - can anyone enlighten?

If really free wheeling, i.e. out of gear with the engine at idle, then this uses more fuel than leaving the car in gear. If the car is in gear, above a certain RPM, and you come off the throttle, then fuel flow is cut off completely.

You can confirm this if you look at your instantaneous MPG display is both situations.

Can't comment on the legality.

If really free wheeling, i.e. out of gear with the engine at idle, then this uses more fuel than leaving the car in gear. If the car is in gear, above a certain RPM, and you come off the throttle, then fuel flow is cut off completely.

You can confirm this if you look at your instantaneous MPG display is both situations.

Can't comment on the legality.

but you'll roll further because there's no engine braking.

not something i'd bother with. for chronic mpg OCD suffers only IMO.

If really free wheeling, i.e. out of gear with the engine at idle, then this uses more fuel than leaving the car in gear. If the car is in gear, above a certain RPM, and you come off the throttle, then fuel flow is cut off completely.

You can confirm this if you look at your instantaneous MPG display is both situations.

Can't comment on the legality.

Yep (Y) Although the engine does slow you down, so if you are on a gradual hill you could maintain constant speed in neutral, whereas in gear you would slow down.

I have heard it's illegal too, but I guess nobody would know!

This morning on my regular 24 mile commute to Buxton I got 48 mpg instead of the normal 44mpg. The only thing I did differently was I kept it in 5th gear up the first long ascent out of Chesterfield.

Pulls fine in 6th up that hill (A619) but would revving slightly higher in 5th really give better mileage? I usually get 53 ish mpg on the return journey as there seems to be so much more "coasting" involved.

Surely if the mpg indicator if put in the instantaneous mode then it would be a simple matter to compare the two readings ? I've always found it is more economical to maintain a steady throttle opening which may result in going down hills a little faster than on the level but this downhill increase helps climb the following inevitable uphill slope.It does however pay not to labour the engine in a too high a gear. I'm amazed in this day of ultra high fuel prices that drivers continue to apply the accelerator on motorway hills in order to mantain speed.

My journey trip mpg has been pretty consistent both ways, on the main road route, for as long as I've owned the car. The instantaneous mpg shows horrendously low and varying mpg climbing the hills ,low 30's at best- but no obvious differrence in 5th or 6th gear. Talking about 2100rpm in 5th versus just under 2000rpm in 6th IIRC on the first long hill . By coasting I mean in 6th gear and foot off the accelerator. I've tried it in neutral but no improvement noted.

[Overall full tank mpg has not varied much at around 48mpg. Worst ever was 44mpg (first full tank) and best 50mpg, going to Heathrow and back.

]

Today I tried the same tactic but was baulked by slow moving vehicles later in the trip and was forced to use 4th gear instead of 6th on the flatter sections.

Still got over 46mpg though.

The A619 and other roads towards Buxton are still badly potholed- some have been patched but not all.

Edited 7 May, 201016 yr by gregoir

Bloody hell! low 30's as a rule 35 on a run.

Yep!

More like high 20s for me, and 35 or so on a run....

I can normally get on a long run 53-55 mpg on motorways in my Octy at "the legal limit!!!" but on a mixture of A roads and Dual carriageways up to the inlaws I can manage up to 57 or 58 depending on what traffic there is and if I get a straight run through.

That's the nub of the problem. I can not do any better. Even when trundling across the flat lands of south Lincolnshire and Norfolk I could not crack 48mpg or so even at a steady 50mph or so. So frustrating these claims of much higher mpg on every forum.

That's the nub of the problem. I can not do any better. Even when trundling across the flat lands of south Lincolnshire and Norfolk I could not crack 48mpg or so even at a steady 50mph or so. So frustrating these claims of much higher mpg on every forum.

It is odd. I think diesels sometime seem to take 10 or 20,000 miles to run in. My A4 seem to continue to get better until around 50,000 miles where it settled down to around 55 mog on a run. Current 140 DSG Toldedo averages 49 mpg but then it is taller and heavier that the A4. The TSI engines have closed the gap better diesel and petrol, Diesels need a quantum change in technology ie go 2 stroke or something to kick on in improved fuel consumption.

Edited 8 May, 201016 yr by lol

That's the nub of the problem. I can not do any better. Even when trundling across the flat lands of south Lincolnshire and Norfolk I could not crack 48mpg or so even at a steady 50mph or so. So frustrating these claims of much higher mpg on every forum.

I'm with you mate, I've managed 52.4 on a run before. I was in traffic at 45-50mph and I was in top feathering like nothing else. One thing I have noticed though the car is returning around 46mpg with a varied drive. As soon as I hit the motorway its more like 42-43mpg. The 50mph limited section of the M1 from Junc 25-28 returns 49-50 in the Octavia, the car is remapped. On the same section of road my Old Ibiza FR (also remapped) returned between 69 and 75mpg. Yet on varied driving it returned 50 or just over. So what I am trying to say is the PD170 appears to be pretty good on fuel with sensible driving, but it doesn't reward you particually highly if you drive it like an anal eco warrior, unlike my old Ibiza. For that reason I just drive it briskly, but sympathetically to my wallet and return 46- 47mpg. I play hockey at the weekends though and the car gets 4 men and luggage and a blast down a motorway to a game in convoy. This has meant my average fuel consumption over the last 3k has been reduced to 44.2mpg.

I have thought about the DPF removal for peformance and economy improvement, but its a bit of an unknown.

Just as a point to think about, engines efficiency is by definition at its highest at peak torque............