ausold

Hi

Can some one help me to get some fuel reading off their Q7 3.0 TDI.

I have a 2010 Q7 3.0 TDI and in the last 6 months or so I noticed a bit of increase in fuel consumption. Was averaging 11.38 lt/100for the first 18 months or so, the last 5 months it average 12.72 lt/100km. This is mostly to and from home and office. What I noticed is that when cold (first 15minutes of starting, the fuel use reading is 1.1 - 1.4 lt/100 and just a bit over 600 RPM when in D (Drive) but stationary, after 15-20minutes, it increased to 1.7 - 1.8 and just under 800 RPM on the Tachometer.

I dont think the RPM should increase when engine warmed up like that, it should be the opposite when looking at other car (using petrol as suppose to diesel). This would explain the increase in fuel used.

Much appreciated if any one who has the same model to check for me if their fuel reading and RPM varied like mine.

Jusforfun

Taking a wild guess here, you are in Canada? and the diesel powered aux heater has been in use over the cold weather causing an increase in overall consumption. Summertime will give better results. Short journeys will cause it to activate more and the metering has to make updates.
It generally runs for about 6 to 10 mins.
I am not sure how they correct for the diesel used by aux heater but I am willing to bet thats why you are seeing a report of increase after warm up when it should be the other way around. I think you will have to factor in journey length and temperature and base your calcs over longer periods.

ausold

Hi Justforfun

I am in Sydney Australia and it doesn't get very cold here, the fuel figure I shown there are actually the last 6 months of summer and autumn driving so it should not need much preheat for the diesel. I am looking for comparison of the RPM and instant fuel reading for the first few minutes and that after 20 minutes. I had the car for 2 1/2 years now, just that the last 6 month I noticed the increase in fuel consumption from the average 11.3 for the first 2 years but that increased to 12.8 in the last 6 months. I took it up with service center but they said they can't find anything wrong with the car. The car is use for to and from work mainly with occasional trip out of city on highway. Most trips are 45-90 minutes due to where we live. I am very light on the pedal and no aggressive acceleration or braking :-)

Like most service centre they don't want to fix anything unless it is obvious and easy but under warranty and tricky to find, it would be "it's working as per specification" it would be good to get some feedback from around the globe as Australian market is very small for these car

Cheers

Jusforfun

The Aus-old should have been a clue. Bang goes my theory. So assuming now its warmer instead of cooler does your idle speed vary with climate control setting?
Do you keep your car under any shade? Is it in shade at work?

ausold

I do not use the aircond much as most trip are around 9-10am and 6-7pm which is generally cooler part of the day and we had a mild summer this year (more rain than sun). If I had it on, the fuel use would be an extra 0.5lt. Car is always park under cover. Its a sudden jump in RPM rather than a gradual one after 10-20min. I dont think its relate to the outside temperature much, today garage temp was 14 degree celsius whereas outside temp was 10 celsius this morning, this afternoon it would probably 16 in the underground carpark at work and 16-18 celsius outside.