Hi Guys

I've been doing my homework on the superb combi (tdi 125kw) vs the VW passat. Both are similar size/shape/weight and have the same engine and driveline. Yet there is a marked difference in claimed fuel economy.

I am comparing the 125kw tdi versions with 6 speed manual and 2wd. The MY12 passat allegedly gets the following:

Urban 5.6 l/100km

Ex urban 4.2 l/100km

Combined 4.7 l/100km

The MY12 superb gets on the same test:

Urban 7.5/100km

Ex Urban 4.8 l/100km

Combined 5.8 l/100km

These are quite large differences. Does anyone know why? I was wondering if there is a gear ratio difference between them?

Can anyone with a current 6 speed superb let me know what the 100km/h (63mph) crusing rpm is and what the computer thinks the fuel economy is on a flat road?

Does anyone know of a spec document that lists the gear ratios for either of these cars?

I live rural, most of my driving is open road and I like the skoda more in every way except the claimed fuel economy.

Cheers.

I have the 103kw (140hp) CR diesel and at 100km/h it is probably cruising at between 1,500 and 2,000, can't remember the exact figure but will have a check on the way home tonight!

Like many others on here, we track fuel economy either via Fuelly or spiritmonitor - my Fuelly details are below in my sig. If you go into Fuelly you can search by car and get a better comparison on economy for the 125kw (170hp) engine.

Does the new Passsat have start/stop technology that is making the difference as that is not yet avaiable on the Superb.

That will make a difference in the way the values are calculated, but everyone I have spoken to has switched start/stop off, thus making a mockery of the way fuel consumpsion numbers are calculated.

My 2003 Passat 170bhp manual average 43.436 over 60K miles (6.505/100km)

My 2009 Superb Combi 170bhp (DSG) averaged 46.793 over 60K miles (6.513/100km)

My 2012 Superb Estate V6 - let's just say it likes fuel a lot

I put the differences down to advancement in engine technology.

Yes the passats do have start/stop. But would they make any difference in the standard tests?

I have been following the fuelly etc results, but the big part I don't know is the driving style that results in that economy and how it will relate to mine. For example we have much lower speed limits here than in the UK.

Do they have the same tires and same tire pressure? Are they using the same diesel from the same gas station? Do you change gear the exact same way? All these factors can have huge difference in consumption.

Yes the passats do have start/stop. But would they make any difference in the standard tests?

Start/stop systems ONLY make a difference in the standard tests. In real life temperatures are lower (start/stop systems only work when the engine is on the right temperature), people spend a lot less time idling at traffic lights, and a lot of people switch these systems off, since they are a real killer to the life of some critical engine components (turbo charger, head gasket etc).

That's why the Passat has a lower official fuel consumption than the Superb, but in real life there will be no noticeable difference.

I guess I need to work through the standard tests and see how much idling time is in them. If they were using 1 litre/hour idling and it's idling for one minute that would be about 17cc of diesel . The 4km driving (allowing 20km/litre) would be approx 200cc of diesel so there is 10% max saving. Yet the passat is doing 25% better on that test.

Are these charts accurate: http://www.dieselnet...es/ece_eudc.php

I'd expect with the extra-urban test that idling time is insignicant, yet on the extra-urban tests there is still 15% difference between the two cars. This is why I am wondering if gear ratios are different. I did read somewhere that gear ratios are prescribed for those tests. So even if there is a better gear choice for part of the test, the tester isn't allowed to use it.

My driving is mostly open road and the enforced speed limit (and hence the typical cruising speed) is 100km/h. If I can get some samples of the fuel consumption readouts in 6th gear at 100km/h it would help greatly. I have these figures for other cars so it is the best comparison I have.

Cown, yes all those factors are prescribed for the tests.

Edited 4 May, 201214 yr by Kiwibacon

95% plus is purely down to how we all drive. I can get near to 60mpg (it is 8 years old and that mpg is around town) out of my wife's Yaris yet she struggles at below 55mpg. At the moment after near 300 miles and again around town I am averaging just over 47mpg from new. Possibly going to Scotland next week so will see what that does to the mpg.

That's the idea behind the 100km/h flat cruising figures I hope to get. They are independent of how you drive.

Urban driving depends greatly on who and how. But on a flat motorway the only things that matters are the car and how fast it is travelling.

I heard somewhere that the gear you must use according to the test can be ignored if the car has the display in the instrument pack that tells you what gear to use, and you use the indicated gear. That might explain it if Passat has it and Superb doesn't.

I heard somewhere that the gear you must use according to the test can be ignored if the car has the display in the instrument pack that tells you what gear to use, and you use the indicated gear. That might explain it if Passat has it and Superb doesn't.

My Superb has the gear indicater.

That's the idea behind the 100km/h flat cruising figures I hope to get. They are independent of how you drive.

Urban driving depends greatly on who and how. But on a flat motorway the only things that matters are the car and how fast it is travelling.

It all depends on your right foot and especially anticipation even on motorways.

My Superb has the gear indicater.

That's the idea behind the 100km/h flat cruising figures I hope to get. They are independent of how you drive.

Urban driving depends greatly on who and how. But on a flat motorway the only things that matters are the car and how fast it is travelling.

It all depends on your right foot and especially anticipation even on motorways.

If you apply more right foot, then you end up going faster than the 100km/h I'm asking about. No?

I'm still hoping someone can supply some figures for me.

That's the idea behind the 100km/h flat cruising figures I hope to get. They are independent of how you drive.

Urban driving depends greatly on who and how. But on a flat motorway the only things that matters are the car and how fast it is travelling.

That's if you ignore the weight of the car (and driver) and options (and fuel), the number of passengers, the load in the car, the tyre pressures, the road surface, the ambient temperature, the weather and wind, the time since a service, the options in use loading the engine, etc!

But on a flat motorway the only things that matters are the car and how fast it is travelling.

Unfortunately it is not that simple. There are (at least) these factors that have great influence:

1. Wind (speed and direction). Around 100 km/h wind resistance is much higher than the rolling resistance (about a factor 2.5). If you're traveling into a 20 km/h wind, the power needed to overcome the air resistance increases by about 75%. So wind speed and direction is a major factor.
   
2. Tyre size, pressure and type. My car has very economical Michelin Energy Saver tyres in 205/65R16. This saves a lot of fuel compared to a wider, less optimized 225 mm wide tyre.
   
3. Driving in very busy traffic or on an empty motorway: If you're driving in very busy traffic (at a relatively constant speed), this traffic will generate a "tunnel" of wind, in the traffic flow direction. This will save a lot of fuel. On an empty motorway this does not occur, so than your fuel consumption will be higher.
   

Edited 5 May, 201214 yr by andrehj

...and don't forget the rain...it can cost you a load of fuel at motorway speeds, as I found out a couple of weeks ago sploshing down the M1 for 100+ miles in heavy rain. My round-trip mpg was nowhere near where it should have been.

I would expect if someone were to give me figures in a blowing head/tail wind or pouring rain that they would mention that.

Likewise if they suspect their car is burning off the DPF (rise in fuel consumption on a flat road at steady speed) I'd expect them to notice and provide the figures either side of the burn.

I am not new to fuel consumption readouts or indeed the factors affecting it (LRR tyres compared to underinflated conventional tyres are maybe 5%, weight effects are smaller again on a flat road steady speed). These will all fall within the statistical spread). I'm just trying to get some numbers at a specific speed on a flat road. If I am able to get a best case and worst case figure from the results (heavy car, chunky flat tyres, cold weather) to compare to a best case (LRR tyres tight, empty car, hot weather, smooth road) then that would be even better.

Can anyone help me out?

IIRC there have been some upgrades in engine management to enable better fuel economy on the Passat.

The Passat also has energy recuperation from the braking system, as standard, as per the Superb Greenline models. This could help during acceleration of which there is quite a bit in both test cycles. However, if you read http://www.telegraph.co.uk/motoring/green-motoring/9241054/Fuel-economy-why-your-car-wont-match-the-official-mpg.html from just a couple of days ago, it seems doubtful that you'll see all the benefits from a lab test in real world mpg figures.

And again at the end of the day it will still come down to ones right foot.

And again at the end of the day it will still come down to ones right foot.

The right foot is the one thing you can take out of the equation; we're talking constant speed - just set the cruise control.

I suspect aerodynamics and weight must play a bit of a part too?

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IIRC there have been some upgrades in engine management to enable better fuel economy on the Passat.

Quite possibly and this is what I would like to test. A few numbers from each car of rpm and fuel economy at 100km/h flat cruise and I'll know.

I suspect aerodynamics and weight must play a bit of a part too?

Unless you are running a roof box, there is less than a percent in it aerodynamiclly. Between the different bodies in passat and superb there are only a few km/h difference in top speed, which means they are all very very close.

Weight isn't a factor in flat road cruising economy. It is in stop/start, but I'm not asking about that.

The right foot is the one thing you can take out of the equation; we're talking constant speed - just set the cruise control.

Thank you.

Edited 6 May, 201214 yr by Kiwibacon

Why don't you have a look on Fuelly.com...although most accounts do not say exactly what engine they have you won't find many Passats anywhere near their claimed mpg figures.

These 2 are for the 103kW variant but I think the test figures are the same although real-world figs will depend on size of right boot.

http://www.fuelly.com/driver/topeju/passat

http://www.fuelly.com/driver/mboberg/passat

There isn't much evidence on Fuelly to suggest you'd get anywhere near the claimed test mpg figures.

Why don't you have a look on Fuelly.com..

Fuelly.com won't tell me how much fuel they use on a flat road at 100km/h.

My usage is very different to most others, which is why I'm looking for a specific test (100km/h cruise) for these cars. I'm hoping as the commuter week starts some people can test this for me on the way to or from work.

Ok passat cc 2.0 tdi 170 bluemotion tech.

Cruising at 63 mph speedo on a flatish road over 10 mile gave 59mpg indicated. It overeads slightly so probably about 56mph.

Was at 1700 rpm