Fuel Consumption on 3.0

[Harrybob]

The issue I have with mine is the fuel consumption rate is substantially higher say with a cold engine idle if my car has just only travelled less then 20klm but after having travelled this distance the fuel consumption during cold engine idle would be much lower.

[GTbee]

Ive just had my 50k service at a dealer. I advised the service guys that my consumption had been high. Everything was done as per the schedule including the upper engine flush etc. The ECU was reset and no faults were found. I did a longish trip (around 60kms return) and the comsumption average as per the computer gradually dropped from 15.8 where it had been to about 14.4, which is still too high. I was advised the oxygen sensors were OK but I wonder if they really do test them.

Today I did a shorter trip and the average crept up to the mid 15s again. How long should I expect to see significant economy improvements?

BTW the car's performance since the service has slightly but cleary improved, not that it had deteriorated as the fuel economy had over the last few months.

[Blitzen06Wgn]

I suggest once you get out on to the highway and the engine is hot try resetting the trip meter and then see what mileage you get from there. Any freeway trip should yield single digit l/100km.

Also remember it's more economical to travel at 80 km/h than 110.

[scottb721]

My 70ks per day in 80 and 100 zones return me an average consumption of 9.4. We don't have traffic lights, only roundabouts, so this helps. If I'm getting up it a fair bit I get closer to 10 avg.
Even when i tromp it after leaving the servo and having reset the trip meter the avg quickly drops from 18 odd down in to the 9s. When putting along doing 80 it sits on about 7 instantaneous.

I noticed too that the aircon adds 1L/100, more than 10% in my case, when the compressor is engaged.

[bates91]

just finished a 2 month stint down at the snow, 9300kms of driving (syd-> jindabyne a few times, down to melbourne, and lots of days of driving up and down the mountain to perisher (60km round trip, 700 or so vertical metres difference)
averaged spot on 10.0 L/100km for the whole journey

[KiDo_Tuning]

The problem with the H6 is the stock DBW and cam timing, the DBW ramps up to quickly while the AVCS does not have enough overlap at highway cruising speed to promote EGR.

[Blitzen06Wgn]

The problem with the H6 is the stock DBW and cam timing, the DBW ramps up to quickly while the AVCS does not have enough overlap at highway cruising speed to promote EGR.

Sometimes i think it would be just easier if the car had a throttle cable...

[KiDo_Tuning]

The problem with the H6 is the stock DBW and cam timing, the DBW ramps up to quickly while the AVCS does not have enough overlap at highway cruising speed to promote EGR.

Sometimes i think it would be just easier if the car had a throttle cable...

Not needed, DBW can always get better fuel economy if the tables are right.

[Mateusz]

I just did a trip from Wallaroo to Adelaide and averaged 8.2L which I'm pretty happy with considering it was 110km/h most of the way with quite a few overtakes. I wonder how much better it would be going 80-90km/h. Does anyone know what the most economical speed is? I kinda wish 6th gear was a bit longer as well. Sits at about 2700rpm at 110. Some small 4 cylinder cars sit at lower revs at that speed.

[bates91]

Does anyone know what the most economical speed is? I kinda wish 6th gear was a bit longer as well. Sits at about 2700rpm at 110. Some small 4 cylinder cars sit at lower revs at that speed.

probably 80km/h or something haha, definitely need a longer 6th gear for better economy

[Blitzen06Wgn]

80km/h is generally proven the most economical cruising speed. Above that wind resistance builds up and sapa economy. You can sort of prove it with the instantanous readout.

[GTbee]

I am now running new oxygen sensors which I installled on the weekend. My suburban economy with plenty of soft peddling had settled to around 15.2 after my recent 50k service where nothing was found wrong with the car.

Tonight I went on a freeway drive for around 120km, averaging 115 kmh and 11.2 l/100l. I was running 98 and I reset the trip meter.

I dont know if the lower figure is mostly attributle to the longer drive or to the new sensors, or both. Similar freeway driving when I bought the car over a year ago netted an average of around 8.0 l/100 km so Im obviously still not happy.

I dont know how long the ECU takes to "learn" that new oxygen sensors are fitted, and then serve to run the engine more efficiently.

[Blitzen06Wgn]

Sounds frustrating. It is possible you're actually getting better economy but the ecu says otherwise. It could be something to do with how it is measured. You could check it with the old fashioned way, fill up, drive for 250 - 300 km, record the distance and then see how many litres it takes to fill up again.

I assume you're running 32+ psi in the tyres and checked the exhaust for any problems, air cleaner is good, hand brake releases properly etc.

[GTbee]

Tyre pressures checked last week, air filter changed at recent 50k service. Cant smell any exhaust leak and I can roll car on level ground without too much difficulty.

I have found the computer to be pretty accurate for average usage as I always do a manual check as suggested.

As I mentioned in the O2/AFR thread I dont know how much time it takes for the full benefit of a new sensor to be realised

[KiDo_Tuning]

Tyre pressures checked last week, air filter changed at recent 50k service. Cant smell any exhaust leak and I can roll car on level ground without too much difficulty.

I have found the computer to be pretty accurate for average usage as I always do a manual check as suggested.

As I mentioned in the O2/AFR thread I dont know how much time it takes for the full benefit of a new sensor to be realised

Disconnect battery, put foot on brake pedal for 5 seconds, reconnect battery and the ECU will start self learning straight away