Best fuel economy at 80mph - 1.6 TDi or 2.0 TDi?

[silver1011]

The vast majority of my commute is at motorway speeds, which for me is somewhere between 70-80mph.

Doing 165 miles a day means fuel consumption is key to keeping costs down.

I know smaller engines generally offer better fuel economy at slower speeds but once you creep up over 50-60mph it soon plumits.

Taking purchase price out of the equation and assuming the engine is in an Octavia (non-Greenline) which would have the lowest fuel consumption for my commute?

1.6 TDi CR105 (5 speed manual) - combined 62.8mpg

2.0 TDi CR140 (6 speed manual) - combined 58.9mpg

Thanks!

[dstev2000]

Seeing as the 2.0 has the six speed box I would assume 6th is taller than the top cog in the 5 speeder.

The larger engine will run at lower RPM at motorway speeds if the ratios are different which could result in better high speed fuel consumption.

Consumption aside, the 6 speed box will also offer a more relaxing motorway cruise.

[Phil-E]

I think the 1.6 has a really long 5th gear. Think it may be the same as 6th in terms of revs at 70mph.

[booke23]

Seeing as the 2.0 has the six speed box I would assume 6th is taller than the top cog in the 5 speeder.

Not necessarily. On my 1.9 TDI Fabia, 2200 rpm in 5th gives 70 MPH indicated.

In the 6 speed DSG Octavia, 70 MPH in 6th is about 2200 rpm.

Unfortunately I can't really add anything to the original question.....My 1.9 TDI Fabia is certainly more economical at 80 mph than the 2.0 TDI Octavia, but it's a smaller lighter car.

However I think the 1.6 TDI would perhaps edge it on economy at 80 mph compared to a 2.0 TDI.

Edited 5 January, 2013 by booke23

[Davidsr20]

The 1.6 cr tdi is not all its made out to be, my parents and my brother both have 2 11 reg octavias with this engine and struggle to get 55mpg ,my vrs is nearly as good (50mpg) and u have the power to go with it! U need the 6 speed box for motorways really.

[Sugar]

I agree with the above poster.

I do regularly do longmotorway trips of150 miles plus early on a weekend. Will just set the cruise at 80 and with little traffic can

Aintain the speed for around 90 percent of my journey.

My maxidot will show an average mpg of between 47 and 49 mpg, never had above 50 at this speed with long continuos spells of motoring,

Have had the car and have completed 20 k miles.tank to tank average is running at 52mpg

[booke23]

My maxidot will show an average mpg of between 47 and 49 mpg.

You'd need to verify those figures with a few brim to brim calculations, as it's common for the trip computer to be inaccurate.

If those figures are accurate, then that's still considerably (10% ish) better than my 2.0 TDI at 80 MPH.

[nickguzzi]

Diesels are most economical at lower speeds. As engine speeds increase the efficiency decreases. At max revs they are likely to be no better than a petrol. This is why trucks have ever increasingly powerful engines, they can cruise at governed speed with minimal throttle.

So a bigger engine should pull higher gears at smaller throttle openings, all things being equal.

Its actually quite complicated as other forces start to factor in. By 80mph, aero drag is significant, tyre drag will be increasing, general engine condition will play its part, as will all the other bearings essential to minimal resistance.

[silver1011]

The reason for my opening post is that my current 2.0 TDi PD170 vRS is averaging 48mpg on my commute (which is 165 miles, most is at 70mph, sometimes touching 80mph and a little bit at either end between 50-60mph. No urban, stop/start at all), which I'm quite happy with considering the performance. This is calculated manually (brim to brim) and is my average over the last 12 months / 30,000 miles.

Due to a number of different reasons I'll likely replace the vRS in a few months from now.

1) I'd be willing to sacrifice performance by moving to the 1.6 TDi on the assumption I would save money on fuel.

2) If the savings with the 1.6 TDi aren't achievable/realistic for my commute then I may as well look for a more desirable 2.0 TDi 6 speed instead.

Availability on the 1.6 TDi is huge and would make it easier to negotiate come the time compared with hunting down a 2.0 TDi.

[dbayman]

I have a 2.0 140CR and the combined does average out at about 58mpg measured brim to brim. (Tank range is typically 600 -750 miles)

At 70mph the rev counter is reading 1800rpm and if you cruise at that on the motorway you should be able to top the 60mpg no problem - at 80mph you are nudging over 2000rpm and you will probably be in the 50s for mpg.

Winter driving with temperatures below 5C you will possibly get 5% to 10% lower mpg on short journeys.

The onboard computer display reads 10% high - think thats the norm for Skoda to make you feel good

[booke23]

I work with a guy with an Octavia 1.6 TDI greenline, and he is getting 62 MPG on his 60 mile round trip motorway commute. Don't know what speed he cruises at, but he used to get low 70's MPG before, in his words "I stopped driving it like a tool"

I know another guy with a 1.6 TDI greenline Superb, and he gets 62 MPG too, but he does alot of long motorway trips at 65 mph.

Downside is, I suppose the greenline is pricey compared to a standard 1.6 TDI.

[James I]

We have an Audi A3 with the 1.6 CR tdi engine and a 5 speed box, as the smaller engine has to be worked harder to move the car, fuel economy is dire! Craig is achieving an average of 44 mpg in the A3, I have 2.0 170CR Yeti, I also achieve 44 mpg average as the Yeti doesn't need to be worked through the gears like the A3.

So I would stick with what you have and drive 5 MPH slower, this will make next to no difference to your journey time but your fuel economy will greatly improve.. I drove to Heathrow in the Yeti at 60 mph and achieved 58.8 mpg! Takes a bit of self discipline though.

[silver1011]

Haha, I know what you mean, every so often the lengthy commute gets to me and I just sit at 60mph with the lorries which gets me into the early 50's.

It lasts for a week or two and before I know it I'm back up to 80.

Wierdly the maxidot under reads and consistently shows my average at 42mpg, even though I know it's actually 48mpg.

[k.young]

I would think that the 140CR would be the best of both worlds.

[SilverSurfer59]

I would think that the 140CR would be the best of both worlds.

Looks that way doesn't it, I have an interest in saving fuel as im a taxi driver.

But after reading posts over the last few months from various owners of the 1.6 I get the impression this engines only going to make some big savings on fuel if you spend most of your time cruising at 40-50mph.

[Gizmo]

The biggest difference in MPG is going to be your speed, as you have found out, drop your speed by 10mph and expect to see around a 10mpg increase.

Cruise set to 75 and mine shows approx 45mpg (calibrated maxidot so it is now accurate)

Cruise set to 65 and I can get 55 - 60 mpg.

This is in a 170CR Superb Estate.

[SilverSurfer59]

The biggest difference in MPG is going to be your speed, as you have found out, drop your speed by 10mph and expect to see around a 10mpg increase.

Cruise set to 75 and mine shows approx 45mpg (calibrated maxidot so it is now accurate)

Cruise set to 65 and I can get 55 - 60 mpg.

This is in a 170CR Superb Estate.

And the moral of this story is PATIENCE is as much a factor as having a potentially economical car when it comes to achieving high mpg! :p

I just don't have it in me, always in a rush. I'm sure it'll come as I mature.

Nice to see such a big car as yours being capable of high mpg

Edited 6 January, 2013 by SilverSurfer59

[gregoir]

Load carried, wind etc makes a big difference as well. I do always check mpg full to full as well as from the compeuchter (little difference in my car).

Anyway, in France fully laden with camping gear and two pushbikes on the tow hitch got around a scary 38mpg at a true 80mph (130kph) on the French autoroutes. Saw a steady 27mpg when running at a steady 100mph on the unrestricted autobahn later in the holiday. So speed is a big factor.

In UK at a steady indicated 80mph (true 77mph) I have got 49mpg on long motorway runs up to Dundee . Can get 50mpg but have to keep to a true 70mph.

[Tony Ramsdale]

Just wondering if skoda will do same as the new golf.........mark 7

Fit the 7 speed dsg to the the 1.6 110 bhp diesel.......

this surley would do more mpg than both above

[dstev2000]

There is going to be a Greenline Octavia 3 with 89g/km CO2 and 110PS plus silly MPG (over 70mpg IIRC), not sure if it will feature the DSG to achieve these impressive figures or not.

[Kiwibacon]

If the engine was the only difference, I'd still expect the 1.6 to win by at least a few percent. But won't the 1.6's also have other advantages like skinnier tyres, small aero mods and less overall weight?

There are people getting terrible (relative) economy from the 1.6, but I wonder if these same people can get terrible economy from any diesel?

Dstev, DSG only gets better economy on the fuel economy tests. At cruise it's got more internal drag and has to run hydraulic pumps etc. Manual gearboxes are the most efficient and always will be. It's the control system on manual gearboxes that often lets the side down.

Nick, diesels are most efficient at highest load. It's far better to pull the highest gear possible around the max torque and use as much torque as possible rather than using a lower gear and more rpm.

This is where petrols suffer. Near max load petrols hit enrichment and poke fuel straight out the exhaust. Their efficiency plummets. So on a petrol there are many circumstances where a lower gear and a few more revs can save you fuel. But not on a diesel.

You'd have to be driving a petrol very carefully and a diesel very badly to get equal fuel consumption.

[booke23]

If the engine was the only difference, I'd still expect the 1.6 to win by at least a few percent.

That would be my gut feeling also.

There are people getting terrible (relative) economy from the 1.6, but I wonder if these same people can get terrible economy from any diesel?

Very good point. We need to hear from someone who owns both a 1.6 and 2.0, or someone who has recently changed their car from a 2.0 to 1.6, so we can see like for like figures.

Edited 6 January, 2013 by booke23

[dstev2000]

Dstev, DSG only gets better economy on the fuel economy tests. At cruise it's got more internal drag and has to run hydraulic pumps etc. Manual gearboxes are the most efficient and always will be. It's the control system on manual gearboxes that often lets the side down.

My reference to DSG was in relation to the new Octavia Greenline, its quoted 89g/km and the possibility of it coming with DSG. It will return better test figures at 56mph. Somehow I don't think they really worry about the figures at 80mph.

[marcusthehat]

Having belted up to Whiteabbey and back yesterday, a return trip of 95 miles, with a 3 Hr lunch in the middle, mostly at an indicated 80 once on dual or M way.

Only 30 odd miles restricted to 60 mph, 15 at the start, & 15 at the finish

Overall speed from key turn to key turn, incl getting parked at both ends.

56mph

at an indicated 49.?? mpg less 3% from previous brimmed calcs (and that is generous) and winter figs.

1.6 TDI DSG Hatch with 2 up

[ianbenny]

I get 56 mpg out of my 1.6TDi, using fuelly to keep a track, this is 50miles per day, 50% motorway 50%A roads between 50 and 65mph(cruise on where possible). I perhaps would like to go faster on the Mways but I find that the car is a bit 'bouncy'.

The tyres are at the specified pressure. I find that torque wise, the 1.6 is poor, and will not respond if you try to move in a too higher gear,especially around roundabouts, but I find it pretty quick off the mark acceleration wise.(Ist gear is pants anyway)

I did find a big difference after I took it to France last year, I think the ECU adapted to a diferent driving style, althought the average mpg went down by about 5mpg and never recovered, but it was much quicker up the gears. (When I first got the car I was getting 60mpg +)

I would definately go for the 2.0TDi next time.

Edited 7 January, 2013 by ianbenny