Best Fuel Consumption for 103/125kw TDi's on longish trips

**OilBurna** · 04-08-2008, 08:15 AM

Went for a nice run down to Geelong Waterfront yesterday, traffic reasonably light on the way down (people driving less?) and medium on the way back. Trip started at Ivanhoe (Eastern subs) onto Eastern Fwy, Hoddle, Swan St Over the Yarra and onto the Westgate

Set Cruise at exactly 100kmh on way down.

Stopped for lunch at the Watershed on the Geelong waterfront (busy and can be slow) but food is good

End result from the trip computer: (not sure how accurate)

5.1l/100km way down, 5.2l/100km way back.

Had a reasonable run with the lights etc and used reasonably gentle acceleration although not slow, 3 adults and one child in the car, climate control on, car has done about 13,500kms so run in.

Pretty happy with that uses less than half the fuel my friends new Landcruiser 200 series does (its a 4.5 litre Twin Turbo V8 diesel)

I'm hoping to break into the 4's on a longer run.

**STV4SYT** · 04-08-2008, 10:40 AM

I can usually get it down to 4.9 on the geelong run, thats until the first set of traffic lights then it creeps up again. i usually sit with the needle dead on 110 which equates to exactly 103 km/h according to the onboard diagnostics and GPS. thats 2 people with some crap in the boot.

**drbass** · 04-08-2008, 05:00 PM

I'll be trying the Geelong run on Friday.

Went to Winton yesterday (from Greensborough). Going up it was 5.9, coming back 5.4.

That's doing 102 in the 100 zone, and 111 - 112 in the 110 zone (107 and 117 according to speedo, corrected values from Garmin Nuvi). Cruise control all the way.

I'm reasonably happy with that BUT the computer (as already mentioned in other posts several times before) is about 10% optimistic.

I ended up with approx. 505 km on the trip, with 800 still to go according to the computer. Mind you, after driving some 40 kms today in Melbourne that has corrected itself to a more credible 650.

Steve, I would expect your Golf is more fuel-efficient. The Passat is a rather big car which people tend to overlook at times.

Seeya,
Michael

**snodrogs** · 05-08-2008, 06:14 PM

Originally Posted by steve_tdi

I can usually get it down to 4.9 on the geelong run, thats until the first set of traffic lights then it creeps up again. i usually sit with the needle dead on 110 which equates to exactly 103 km/h according to the onboard diagnostics and GPS. thats 2 people with some crap in the boot.

Do you mean that the GPS speed matches that of the "uncorrected" digital display through the Climate control? If so this means that the actual Speedo itself is significantly incorrect? Certainly reading your post and that of drbass, it seems that way. I haven't got my GPS out to check against my car yet...

I wonder where the odometer mileage actually comes from - the digital display figure or the speedo. (okay, I'm making the assumption that the "time" would be accurate, or relatively close to a known and accurate figure, especially as the CANBUS must need some sort of clock pulse)

And then where does the calcualted l/100km figure come from, and how accurate is it?

Perhaps this leads to the optimistic figures reported??

**R36 Dreamer** · 06-08-2008, 07:12 AM

Originally Posted by snodrogs

Do you mean that the GPS speed matches that of the "uncorrected" digital display through the Climate control? If so this means that the actual Speedo itself is significantly incorrect? Certainly reading your post and that of drbass, it seems that way. I haven't got my GPS out to check against my car yet...

I wonder where the odometer mileage actually comes from - the digital display figure or the speedo. (okay, I'm making the assumption that the "time" would be accurate, or relatively close to a known and accurate figure, especially as the CANBUS must need some sort of clock pulse)

And then where does the calcualted l/100km figure come from, and how accurate is it?

Perhaps this leads to the optimistic figures reported??

My car speedo is inaccurate - at displayed 110km/h the GPS says 102.

The climate control shows the same speed as the GPS when I do that trick.

Funnily enough, I tested the average speed readout, and when I reset the trip computer at GPS displayed 110, and keep a constant speed (hume highway) after a min the average speed matches the GPS

So that leads me to think the car knows the speed, just that it shows it incorrectly on the analogue speedo. If this is the case, the fuel consumption should be accurate also.

Might have something to do with the uneven increments on the speedo - goes from 20km/h increments to 30 after 80km/h?

My GTI was just as bad. When I took it in for service they couldn't adjust it apparently.

Does anyone have an accurate speedo?

**Jarred** · 06-08-2008, 10:25 AM

Most maufacturors "under" speedo's in thier cars. Most should be between 5-10% off, so the figures seem correct to me. Manufactures do this so people don't complain when they get speeding tickets when they thought they were doing the speed limit, etc etc etc..

Most company's do it, All of my family's cars do it.

**snodrogs** · 06-08-2008, 07:48 PM

Originally Posted by R36 Dreamer

My car speedo is inaccurate - at displayed 110km/h the GPS says 102.

The climate control shows the same speed as the GPS when I do that trick.

Funnily enough, I tested the average speed readout, and when I reset the trip computer at GPS displayed 110, and keep a constant speed (hume highway) after a min the average speed matches the GPS

So that leads me to think the car knows the speed, just that it shows it incorrectly on the analogue speedo. If this is the case, the fuel consumption should be accurate also.

Might have something to do with the uneven increments on the speedo - goes from 20km/h increments to 30 after 80km/h?

My GTI was just as bad. When I took it in for service they couldn't adjust it apparently.

Does anyone have an accurate speedo?

Thanks for the feedback.

If it matches the average speed to the GPS, then it means that the car DOES know the "real" speed... Why not just make the speedos accurate too. What is the cost of this instrument in comparison to the remainder of the vehicle...

I can understand Manufacturers ensuring their speedo are not under-indicating the speeds, but they should be aiming for accuracy surely.

Oh well. Back to sourcing that rattle in the LHS of my dash before it drives me insane...

**Deep Black** · 09-08-2008, 11:11 PM

Can some one teach me the trick to show speed on climate control display?
BTW my new Passat 125KW TDI has the LHS-dash rattle problem as well. It looks the fitting quality is not up to general German standard. Rattle seems quite common in the Passat range.

**vanDub** · 10-08-2008, 04:52 PM

This thread has gone from questioning fuel consumption to disertations on speedo accuracy.

We all agree that the speedo indicates speed higher than true speed to the tune of 110 indicated = 102 true (usually taken as GPS speed). Can we take that as given? I do and just compensate by a comparable amount when I drive or set the cruise control.

As far as fuel consumption goes, the MFD is known to be inaccurate giving a more optimistic value than reality. The MFD value is only usefull for comparing one trip to the identical trip at another time to see if it is better or worse. The only consumption figure that can be relied on is that calculated from fuel added to distance travelled over a long time and preferably with several fill ups starting and finishing with a full tank.

On that basis I got 5.9 L/100km with 95% highway driving on the delivery trip from Melbourne to Townsville after some local running-in around Melbourne. I seem to be getting around 7.5L/100km aroung town on shortish trips but am only on my second tank (I get about 4 weeks commuting per tank full).

The combined country/city figure is 6.7 L/100km which is close to the VW advertised figure so I am happy. I have no intention of doing a lengthy highway trip at say 85 kph in 100 or 110 zones just to get a better figure.

The Passat uses about 60% of the fuel of my other V6 petrol camry which is why I bought it for my long term keeper. The feeling of acceleration that doubles or triples that of the camry plus the sportier ride is a welcome bonus.

**sporran** · 11-08-2008, 03:13 PM

Have only had my 125kw wagon for a couple of months and have been getting around 6.8lt/100km in mostly city driving. I have done less than 2000kms in that time but after about 1000km I have also discovered a rattle coming from the left hand side of the dash. It seems to kick in as the gearbox drops down through 1500 revs. Looks like I'll have to get down to the dealership to sort out?