99 Gu TD42T excessive fuel usage

[stealth12v6]

I know this has possibly been covered before but i have searched and not come up with an answer, anyway ive had my GU Td42T for 3 years and when i first purchased it was returning fuel figures of 16L/100 km which i was really happy with, since then i fitted a roof rack and 2inch lift and fuel usage increased to 18L/100 km which i was still content with, but now without change to the vehicle it has increased to 20-21 L/100 km and that was mainly highway driving 2500 rpm/ 100 km/h (as i dont use 5th gear due to known failures) so im just looking for an answer if there is a possible cause for this increase from knowledgable members with experience, please consider the following,

vehicle and engine has done 240,000 km from new and running factory HT-18 turbo
standard size wheels and tyres fitted 16x8 265/75 16
oil,fuel and air filters changed every 5,000 kms by myself
Valve clearances done and new injectors fitted 12 months ago
I havent checked to see if diesel pump has gauze filter (if a restriction there could be the cause),

Cheers for any practical responses in advance

[threedogs]

is it blowing any more black smoke than normal, might be time for a dyno IMO

[Winnie]

Are you towing?

[stealth12v6]

nah no extra black smoke and previous trip with camper trailer weighing in about a tonne about 8 months ago was 18l/100km over 5000 kms and this weekend just had my 7x5 single axle trailer with a quad bike on it and getting 20-21 l/100 km, also was dynoed 12 months ago when new injectors fitted.

[altech]

Hi Guys , maybe because your just using 4th gear ,not 5th . in your thread I notice your RPMs is high for diesel , here a pic of mine 4.5 petrol at 100k regards Alex

[growler2058]

I thought that the 5th gear issue had mostly been sorted?
I think that it wouldn't hurt to get to a diesel tuner and have them look at it and tune it correctly

[happygu]

I would use 5th gear - keep the revs down a bit, and also the fuel use.....

It seems a little excessive though on fuel use, especially with standard tyres, but someone may have wound up the pump a little before you got it.

I have never owned a ute - always wagons, but the utes always seem to use a bit more - possibly due to the different diff ratios to the wagons

[stealth12v6]

perhaps petrol engine patrols run different gearbox or diff ratios due to the different power/torque curve and as 5th gear isnt on the main shaft its not best to tow in 5th, also as far as 5th gear being sorted unless i strip down my gearbox i have no way of knowing if the upgrade shaft has been installed,,, cheers anyway

[Winnie]

Guys he has always driven like that and has had a recent jump in fuel consumption... It's not how he's driving.
Sorry I can't help mate

[stealth12v6]

its a wagon 56042 cheers anyway guys just thought id throw it out there to see if theyre were any known fixes before i visit the dyno for the 2nd time in 12 months

[katwoman]

It is really high fuel figures. I have exact same car, and fully loaded, big wheels, loaded roof rack I still was getting 14L/100km when we crossed the simpson. Which is excessive for me. At 100 km per hour she sits just over 2000rpm. This is a car that is about to click over 300,000. I think there is def an issue somewhere.. Get it checked out. All I can think of would be injector pump.

[stealth12v6]

Thanks to all who replied much appreciated

[stealth12v6]

all sorted, a tune at MTQ proved a poor tune by previous tuner, fuel economy now reduced by around 5l/100km and still making same power/torque, wont be going back to other place again thats for sure

[Nightjar]

AND use 5th gear, it will also improve greatly.

[Winnie]

Did the fuel increase happen straight after the first tune up? If not then something has caused it to go out of tune significantly and you can't really say it was a poor tune by the last mob.

[Chimo]

Whats the story with td42 gearbox's?

I have a GQ td42 that I turboed back in 92ish and I have run in 5th most of the last 25yrs including when towing a couple of tonnes of boat on the flat and fourth up hills etc

Did the gearbox's go backwards in the GU? What else am I missing?

I get around 11 to 14 lt / 100 on trips and around 16 to 18 / in traffic and with traffic lights of which there are many on the Gold Coast. Have a roof rack but running standard wheels

Chimo.