Old Soldier replied:

G'day Mike,

5.5km/l is pathetic mate. I wouldn't be looking for some magic solution, I would be finding a really good mechanice to rectify that.

Obviously something is wrong somewhere.

As an example I did a 7,500km trip around FNQ and the Gulf area winter this year, pulling a very heavily laden off road camping trailer.

the road surfaces ranged from first class bitumen where I sat on 100-110 in cruise control, ribbon road, formed but rough roads like the Great Top End highway from Normanton through to Burketown, very rough bush roads around Cooktown, and some straight out four wheel drive areas like the Bloomfield Track.

Driving was in cruise, 2WD, 4WD and 4WD Low Ratio in some areas.

Average overall for the whole trip was 7.65km/l.

Considering some of the conditions faced, the speeds driven and the load carried I am reasonably happy with that.

vehicle is 1998 3.5 V6 Jack SE with [then] about 145,000km on clock.

Like I say mate - find a good mechanic, don't look at gimmicks like Hi-clone

regards

Dennis

Mike replied:

Thanks for the reply, Dennis.

The truck has only 15,000 km on the clock. The highway fuel consumption was impressive - especially considering the 3.0 TDI that I previously had generally returned 9.2km/l. Overtaking is magnificently lusty compared to the breathless diesel (despite all the hype on the high pressure diesel).

The trip out of Melbourne (with the trailer) was the Maroondah Hwy leg up to Yea and then Mansfield. It's very hilly and undulating country. Could not hold lock up in fourth and was continually changing down to lug the trailer at 100 km/h. So I'm not so sure it's a tuning thing, otherwise the highway consumption would be ordinary too?? Any other thoughts.
Cheers
Mike

Mick replied:

Mike I think you're right that the fuel consumption on the highway wouldn't be good if there was a problem. I think it's a thirsty vehicle and maybe you'll have to lighten your right foot!!
By the way Melbourne to Mansfield is not really a very hilly trip!!

rodeoowner replied:

Mike I have the 3.2 Rodeo. I get on average 6km/litre and the ute is always fully loaded, so I don't think your figures look too way out.

Savvas replied:

Hi Mike ...

Sorry to tell you this, but 5km/L or 20L/100km is what you are likely to get with the auto 3.5V6 around town. However, it depends on your definition of "around town".

In my (wife's) situation, she does less than 14kms a day going from one suburb to a neighbouring dropping off kids at school and then going to work and back again. This is all done in 4 separate short stop-start trips, where the motor barely gets to warm up. Our usual consumption is somewhere between 4.5km/L and 6km/L or 17L/100km to 23L/100km depending on circumstances. Usually around the 20L/100km mark.

Highway cruising it's a different beast all together. One winter trip from Thredbo to Sydney saw 10L/100km or 10km/L. I can only guess that the cold dense air and a generally downhill run to the coast contributed to such a good figure. Normally on a run up and down the NSW North Coast, it will get around the 8.5km/L or 12L/100km mark.

Resetting the ECM provides a reduction in consumption for about a week, however it creeps up again.

Using 98 fuel gets you a tiny improvement in consumption. On average since April 1 this year, using 98 we average 19.6L/100km and using standard unleaded we average 20.8L/100km. Not quite enough improvement to justify the extra cost of 98.

Ours is a 2000 Monterey V6 with 54000kms. We run BFG A/T's, Finer Filter air filter (single element about town, both elements on any sort of longer trip) and 36psi all round. I find that there is no benefit in consumption by going over 36psi, but there is a definite downside to going under 36.

A friend with his new 2002 Equipe V6 is getting similar consumption figures.

Savvas replied:

PS .... The consumption you achieved with a 450kg trailer on a country run is too high. You may get some gear hunting but not a lot of it.

Is the engine "pinging" under load? If it is, try running something like Wynns Spitfire Petrol Treatment through it. If you do try the Wynns product, then use "Petrol Treatment" not "Injector Cleaner". According to the Wynns website, the petrol treatment is the one-off system clean product whereas the injector cleaner is the ongoing maintenance product.

Redjack replied:

Mike, I've got a '99 3.5 litre manual. Overall consumption over 80 000km is 7.98l/km. Best has been 9.23l/km, light running on open roads. Worst has been 5.95l/km, towing 1200kg camper trailer at 110km/h. Out of curiosity I did the ECM reset, consumption unchanged. Petrol Jacks already have a swirl inducing device in the inlet to the airbox, so I don't think a hi-cyclone would do anything other than restrict airflow further. I had the standard Wranglers on (just replaced 2 after 80 000km with Michelin Syncrones), standard air filter. Pressures are 210/240kpa, as advised on tyre placard on vehicle. I understand the auto's are thirsty in traffic but yours seems a tad excessive, though the open road figure seems Ok. Is the around town figure mainly short trips on cold starts as that really sucks the juice?

Greg replied:

Mike I own a 97 3.5 DOHC Pajero AUTO (153kw). The values you get seem to be similar to mine. My speedo is very accurate at 100 kph which is what I mostly cruise at. On the open road I get between 8-9kpl at this speed and around town about 7kpl. Towing a heavy trailer (1200kg) I get around 5-6 kpl and using a roof rack without towing reduces the values by 1-2 kpl depending on the wind.
My unit is fitted with extractors and a free flow exhaust including cat to give 170kw and a fair bit more torque. The extractors make about 0.5 kpl improvement. I have tried a hiclone and in all conditions they are a waste of time. I recently crossed the Anne Beadell Hwy and got 5.2 kpl whilst the 2.8 diesel (MAN) with me got 7.2 (No roof rack). Without my roof rack I am certain I would have got over 6 kpl and if it was a manual I am sure I could have got 6.5 which looks pretty good against the diesel. I would suggest your figures are average for that type of vehicle. Autos are very heavy on fuel but generally much better off road. Try the extractors plus exhaust if you want an improvement but make sure you get a flow through CAT.

Mike replied:

Redjack/Greg/Savvas

Thanks for yr responses. My round town stuff is similar to Savvas - short trips, no top gear. I'm not sure on what side of a tonne the trailer was. Alleged DRY weight is 450kg, add water in the tank, toolbox, camping crap, tables, chairs, fridge & a fully loaded vehicle and you're prob looking upwards of 3 tonne. Then there's the missus .... but maybe it's safer to blame the trailer. The cruise control only need a sniff of an incline to give it full throttle (delicate device, not), but even using the right foot, it's still a little sensitive. No such problem without the trailer.
Having had the 3.0 diesel, I'm surprised in the capabilities of the petrol and as a non-tow mount, it's my preference!

alex replied:

Mike, I think us V6 auto Jack owners need to just get used to bad fuel consumtion. Mine is bad so I fitted a extra tank for extra range. I will keep my eye on the forum for a miricle solution.

Savvas replied:

There is actually a replacement air filter kit available from Calmini in the USA. The air box is replaced by a pod type filter which then is supposed to give better breathing. But it will be totally useless for any sort of offroading.

I'm also aware of one fellow in the US who came up with a cold air intake for his Isuzu Rodeo (Holden Frontera) and is getting increased mileage. However the intake is now below the front bumper and to my way of thinking is asking for trouble there.

I have been trying to come up with some safe way of getting a cold air intake from behind the top of the grille. I'll post it here if I ever work it out.