Efficiency

Hello Experts and Members,

I own a stock 2009 Wagon with the ZD30 engine. As I live up in the lovely NT where there is hardly any traffic I average about 11L/100KM on average with city/suburb running.

However whenever we go on a trip averaging around 120-130KMPH I end up with a horrible 18L/100KM.

I know this is probably because the diesel engine is revving at almost 3500RPM, but I was wondering if anyone knows at what speed the Inter-cooler Turbo Common Rail ZD30 engine is most efficient. I'm guessing somewhere between the 80-110KMPH zone.

Some insight in this regard would be greatly appreciated. :smiley_thumbs_up:

Have a great day!

Welcome to the forum and yes lucky you living in the Darwin area , our 2002 GU gets the best fuel figures when towing at 2800 rpm .
These things were not designed with your open speed limits in mind but would suggest you do a trial at 110 and see if there's a difference .
My GQ slurps 18 litres a hundred without towing anything but add big tyres a lift and roof rack not to mention all the gear you cram inside our 4bys and it soon adds up at the bowser .

90 - 95 Kph will give you the best economy.

Over 110 it starts to dive off the edge of the cliff.

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Originally Posted by Beetle Rox

Hello Experts and Members,

I own a stock 2009 Wagon with the ZD30 engine. As I live up in the lovely NT where there is hardly any traffic I average about 11L/100KM on average with city/suburb running.

However whenever we go on a trip averaging around 120-130KMPH I end up with a horrible 18L/100KM.

I know this is probably because the diesel engine is revving at almost 3500RPM, but I was wondering if anyone knows at what speed the Inter-cooler Turbo Common Rail ZD30 engine is most efficient. I'm guessing somewhere between the 80-110KMPH zone.

Some insight in this regard would be greatly appreciated. :smiley_thumbs_up:

Have a great day!

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I would imagine you'd have to rev it high to keep it up at that speed constantly, so the fuel economy would suffer.
I reckon at those speeds and relatively higher revs for a diesel rig, 18L/100KM is not a bad outcome.

How accurate was your clocking on two different scenarios btw? Did you use the full tank & 100km & refill method?

On the open road the biggest influence on economy is aerodynamics. Escecially on a wagon as you get a low pressure zone behind you which is trying to suck you back. Think of the turbulence behind a semi at speed. Anything that disturbs airflow (bullbars, roof racks etc) causes low pressure zones that will add drag. Even a lift will cause more drag under the vehicle. And its a square function -- if you double the speed the drag increases 4 times.
Thing to help. A wind deflector at front of roof rack, a tight cover over any load on the roof rack. Wind deflectors at the rear to direct some air across the back window to stop dust build up on the rear also reduce the drag by reducing the low pressure zone.
As GQtdauto said he gets better economy when towing, because the trailer (especially a box trailer or camper trailer will smooth out the turbulence.
Try an experiment, put your hand out the window at various speeds and you'll see how much drag each speed produces.
As a side note this is the reason the USA introduced 55mph speed limit during fuel crisis to try and reduce fuel consumption across the board.

Sent from my SM-T355Y using Tapatalk

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Originally Posted by Turtle_au

On the open road the biggest influence on economy is aerodynamics. Escecially on a wagon as you get a low pressure zone behind you which is trying to suck you back. Think of the turbulence behind a semi at speed. Anything that disturbs airflow (bullbars, roof racks etc) causes low pressure zones that will add drag. Even a lift will cause more drag under the vehicle. And its a square function -- if you double the speed the drag increases 4 times.
Thing to help. A wind deflector at front of roof rack, a tight cover over any load on the roof rack. Wind deflectors at the rear to direct some air across the back window to stop dust build up on the rear also reduce the drag by reducing the low pressure zone.
As GQtdauto said he gets better economy when towing, because the trailer (especially a box trailer or camper trailer will smooth out the turbulence.
Try an experiment, put your hand out the window at various speeds and you'll see how much drag each speed produces.
As a side note this is the reason the USA introduced 55mph speed limit during fuel crisis to try and reduce fuel consumption across the board.

Sent from my SM-T355Y using Tapatalk

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Very interesting post , again I learn something new thanks mate , we were pulling 2.750 tonne of caravan and did not know which gear to put it in or what speed to travel at , soon learned overdrive off 80-90 Ks , fuel consumption dropped and temperatures were much better .

Travelling in a Patrol @ 130 kph will never be efficient or any speed for that matter
slow it down take in the scenery and enjoy the ride.
When Im back on the road Ill be travelling with the OD off and cruise control on lol
love my cruise control

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Originally Posted by threedogs

Travelling in a Patrol @ 130 kph will never be efficient or any speed for that matter
slow it down take in the scenery and enjoy the ride.
When Im back on the road Ill be travelling with the OD off and cruise control on lol
love my cruise control

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Mine doesn't like the cruise on going up anything more than a slight incline , if it's more than a slight incline the cruise shits itself and the check engine light comes on , so I only use the cruise control on the flat stuff .

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Originally Posted by GQtdauto

Mine doesn't like the cruise on going up anything more than a slight incline , if it's more than a slight incline the cruise shits itself and the check engine light comes on , so I only use the cruise control on the flat stuff .

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Mine is an Autron branded one plus I have an auto

Yeah that's the missus GU 2002 3ltr auto but I think the cruise is factory , or at least I thought it was .
The GQ just has a hand throttle for cruise .