HI

i recently bought a vt, just had a major survice,approx 120 000klms and drive untill the distance to empty reached about 10ks. including highway driving and not driven hard. i checked the trip at the petrol station before filling up and i had only just managed 400 ks. surely with a 70 odd litre tank you would expect more. the o2 sensors were changed as they were black, an injector cleaner was run through at service, tyres were correct pressure all with hardly any improvement... wot else could be the problem.

any help would be appreciated

How much fuel is going into the tank when you fill?
Fuel gauges love to play up in these vehicles.
If the car has a vacuum leak the ECU will run an increased fuel trim (open the injectors longer) to compensate for a lean mixture.
V6 engine? Check the purge hose located under the throttle body. Often fall off.
Possibly have a fuel leak. Fuel rails can leak on that model. Check the intake side of the rail.
My VT V6 used to achieve approx 500 km around town, 650km at best on highway only driving.
My VT 5.0L managed 400-450km around town.

yer shes a six banger
you have jogged my memory because the last time i did try and fill up the tank full, not that often these days...i only managed 55-60L . and the guage said it had less than 5k on range. what could cause this?
yep the purge hose has fallen off many times but is on atm.
as for the other stuff you mention i will check out.

The fuel sender card could be reading incorrect resistance.

thanks for your help mate

all appreciated

Hi
This is my 1st reply on here. I have owned eight commodores since '96. A VT Berlina wagon that I bought in 2000 was getting 830k's to a tank. I regularly drove the Hume hwy and checked my odometer with the signed posts and it was only ever out by a half k over 100k. I always used 98 octane and preferably BP Ultimate. I also put in Nulon 80,000 k engine treatment. I put in two Hyclones in the air intake as well. My son has the car now and it has 350,000k's and is still mechanically excellent. The Nulon effect for fuel economy was not really evident until after the 2nd oil change. I have seen this effect on every car that I have used Nulon. When I moved to Qld I was travelling up and down the M1. If the traffic was light, it would average 7.3 L/100k. I did the same to a VY11 Berlina wagon and it was also incredible on fuel. I hope this helps.

Try noting the amount of fuel you pump into the tank....take note again when you refill. This way you will be certain how much fuel has been used. Work out the km's travelled based on this rather than the possibly unreliable fuel gauge.
I recall o2 sensors always being "black" but perhaps too "black" can suggest over fueling.... not neccessarily an o2 sensor(s) fault.
As mentioned below, vacuum leaks will run the engine richer. Leaking or poor spraying injectors won't help...