Fuel Tanks and Fuel Economy

[Big Gags]

Drove up to Bright and back for a four day weekend. Had a big Pelican box on the roof (1240 mm wide, 450 mm high) so aerodynamics weren't great and I also had two bikes on the back but within the width of the car so probably not too much issue there in regards to drag. Had 3 x people and a pretty light load of clothes and some food for the weekend. I have a 2010 ST Wagon with ZD30 engine, 3" exhaust fitted, and a tuning chip (can't remember brand) that I have set to 3 out of a scale of 0 to 9. I filled up both tanks before leaving and from what I could remember the guy I got it from said he had a long range tank fitted. Anyway, I have always thought that the main tank seems to drain pretty quickly on the gauge and I had a theory that maybe the previous owner had put on a long range tank but used the same sender unit and so it was thinking that the tank was draining faster than it actually was. Anyway, we drove up there via the Hume Hwy (sitting on 110 km/h) and Alpine Highway (sitting on 100 km/h) and then did some running around all weekend including a drive up to Mount Beauty to go Mountain Biking. The low fuel light came on at one stage and so I transferred half the fuel from the aux tank and this bought the main up to about half full again. I then decided to see how far we would get once the low fuel light came on. It came on while we were on the Hume and so I kept driving knowing that I still had half the aux tank in reserve. I think I got about 100 km with the low fuel light on and the gauge went well below the Empty marker. Eventually, the engine just stopped running at 110 km/h (it was still spinning due to drivetrain but no power!!). I quickly hit the Aux Transfer switch but was obviously too late and as we coasted to a stop I managed to roll over to the side of the road. I left the ignition on and hit the Aux Transfer switch again and let it run for 5 min or so. I got out and primed the bulb under the bonnet and got back in to try and start it but no joy!! Put the Aux Transfer switch back on and let it go for another 5 min or so and this time managed to start it but it ran for about 10 seconds and then stopped. Tried again but it didn't work!! Was starting to get a bit concerned at this stage so waited another 5 min (transfer speed seems really slow!!) and this time when priming the bulb I used shorter, lighter squeezes until the bulb was pretty firm and then Bingo - she started!!! Went to take off though and got to about 10 km/h and it stalled again!!! Quick read of the manual (last resort) and it said to "race" the engine if there were problems after re-priming the bulb. So I primed again (light squeezes again) and got it started and then revved it out to 3000 rpm about 3 or 4 times and everything seemed OK so we took off and left the Aux Transfer pump on and made it the rest of the way home and by the time I got home the Aux tank was showing empty and the main tank about quarter full.

I went and filled up and the main tank took 60 litres and the aux tank took 70 litres (it was $199.94 but bit of a bonus as the pump price was 4c per litre cheaper than the price on the sign). For the 130 litres of fuel we had done 730 km which works out to be 17.8 L/100 km on average - not sure if this is good, bad, or otherwise in the scheme of things?? I know that the previous owner got most of his mods done by ARB and I just had a look on the website and saw that they do a 70 litre replacement sub tank and so I am assuming that is what has been fitted. I have also read that the main tank has 95 litre capacity although I'm not sure how much of this is usable? The missus was a bit pissed at the 15 min or so on the side of the road but I wasn't too worried as I now know roughly how far I can get on the low fuel lamp and I also know how to get going again if I ever run out of fuel!!

I'm assuming that having the big box on the roof would have a pretty big effect on economy and I'm interested in what others are getting under various conditions - please share!!

[garett]

With a gq na td42 loaded with stuff, 2 adults 2 kids, roof rack about 500mm high right across the rack, was pretty heavy, in steep hills 16l per 100 at 110kmh. ( yes 4th right foot burried). Flat ground i got bout 13 per 100 the same trip. 33 muddies didn't help. This was fairly pushin the old girl. Covered 2500km in 2 and a half days with only one driver. Not sure how good a comparison this is but

[VK2FMIA]

My stock 2005 ZD30 (manual) on standard size tyres averages around 13.5 litres/l00 km. I have a rooftop camper & half roof rack, a 60L Engel, tucker boxes, water & a bit of camping gear in the vehicle all the time. I rarely get above 100 kph as I`m usually on the back roads. The main fuel gauge moves through a quarter for every 200 km of travel. On the odd time that I get it up to 110 kph the fuel consumption increases considerably.

[threedogs]

I get around 13/100 around town and 15/100 towing my camper at 110 kph
I also have 285s in Federal mud which will soon be changed to BFG all terrains
I dont expect those figures to change much.

17/100 in those conditions sounds about right the CRD are a tad thirstier than the Di diesel

[GQtdauto]

Gq gets 20 - 23 ,and three litre GU around 18 towing and not much better round town .

[the evil twin]

Your fuel consumption seems about right.

If your chip is a DP chip then most people I know run them at 6 or 7 (mine I set to 7).

Your factory main tank capacity is approx 90 (long range options are 145 to 150 ish).

Your long range sub sounds right at about 70.

The transfer rate for the factory pump is 1.5 litres per minute.
That means it takes about 20 mins to transfer the factory 30 litre tank.
Most times a long range sub still uses the same transfer pump.
If so that is why you had to spend so much dicking around to get it going again.

EDIT.. as Hodge said... try and NOT ever let your CRD run dry, very bad juju.
The fuel is both the coolant and the lubrication for the pump.
Indeed a lot of vehicle manufacturers with CRD's will cut the engine at low fuel levels so the pump cannot run dry (amongst other reasons).

[Hodge]

Your figures sound consistent to 2010 CRD zd30.
Biggest toll on my fuel economy were obviously the larger tyres , but more so the roof rack.


Also...
You're running the gauntlet letting a CRD pump run dry, especially when hot. They rely on constant diesel flow as a cooling lubricant.

Sent from my SM-N920I using Tapatalk

[Fireblade]

i have a 2008 crd
getting about 15l/100km
i think its high because it use to be better without the roof cage, awning and snorkle. (more air resitance)

also has steel sidesteps, brush bars and bullbar. slightly larger tyres 285/65r17

i does drink more at 110km verses 100km so i sit on 100 mostly.

when i first got it i didnt have roof cage, awning and snorkle. and i was getting about 12L per 100km
air resistance has ruined it id say.

just put new fuel filters in time will tell if it makes a difference haha.