Bad Fuel Economy?

[dantheman85]

So i wanted to know what others get with their fuel consumption?

Ive got a 2009 d40 nav 2.5 diesel with 175000kms 31inch tyres but only get around 550kms to the tank.

Is that normal?

I hear other people that own diesels getting heaps more k's.

My ute runs good and only mainly does highway driving. Doesn't blow any smoke. Ive cleaned the MAF sensor and change all filters on my service and no change in fuel consumption.

What else could it be? Should the injectors be serviced even though the ute seams to run good?

 

[Old.Tony]

As my car's gotten older its fuel consumption has worsened slightly, but we've also moved to a rural area where there's a fair bit of 100km/h driving which does chew the fuel and I've added a roof basket which increases the drag (especially important at higher speeds). I'm getting about 12.5LPHK when I'm being moderate, or 13.5 when I don't care too much and just want to get going. I had gotten 10.2LPHK on a mostly highway cycle, but that was prior to putting the roof basket on.

Towing 2.5T of caravan results in 16s on level ground at 85km/h, up to 21LPHK when there's hills to climb (like heading up to Bathurst).

 

[GunMentalGrey]

How much fuel are you putting back in the tankwhen you fill? 80l tank and i normally fill with under 70l from ‘empty’.

My 2007 Manual ran just under 10l/100km around town prior to bigger wheels and a lift. It’d do between 8-9l/100km on the highway.

Now with 285/70/17 tyres (just under 33” I think) it shows just over 10l/100km, but each wheel revolution carries me a bit further so it’s under that somewhere. I seem to need to fill up around 600km mark on the trip meter. It’ll go to 650 normally, but probably not to 700.

 

[Nisap]

2011 STX 2.5l Diesel (140kw) Auto, 235k on the clock, running Toyo 255/65R17 was getting between 8.2 and 8.6l/100km (Dash Reading), just replaced tyres to GT 265/65R17 and consumption has gone up to between 8.8 - 9.0l/100km (Dash Reading).

Best I ever got it down to was 6.9l/100km but that was when the Nav was about 1 year old on a trip from Cairns out to Longreach and back.

On my last big trip from Cairns to Tasmania towing the camper trailer I averaged out at 8.8l/100km, this was calculated over actual km travelled and fuel used, not what the dash said, although the readings from the dash where around that number over the course trip.

I'm the opposite to you dantheman85, I've always wondered why mine seems to use less fuel than others when reading what others get.

Oh and 2 last things I have have come across when it cones to fuel consumption, I went from the higher average of 8.6l/100km down to 8.2km/100km when I did the ERG blank off / catch can mod. And I only use Caltex Vortex Diesel (where available), a couple of years back I used BP for several tank full's and my consumption went up to 9.1l/100km (no change of driving conditions or average daily distances), quickly went back to using Caltex after that, still unsure why it made such a difference.

 

[Nig]

Make sure your fuel filter is good, Run injector cleaner through it. Mine is getting 11 tot 12 ltrs to the 100ks and most of this driving is up on 100kph highway work. Std tyres at 34psi.

 

[Erick]

2005 3.0 l. Standard size tyres Just did a 3400km trip, last 1400 km was carrying/towing 1500kg. Used 355l fuel. I can get down to 9l/100 km when driving easy-95km/hr.
Driving in ur most efficient rev range 2000-2500 for these engines and keeping the boost below 10 psi makes all the difference. Mine will guzzle fuel if driven fast or carelessly. Putting bigger wheels on does not do much, the engine just has to work harder.

 

[dantheman85]

So this is a screen shot of my average fuel consumption after doing some ‘city driving’

what’s going on here?

 

[GunMentalGrey]

So this is a screen shot of my average fuel consumption after doing some ‘city driving’

what’s going on here?

Poor calculation in the scanner? My cheap OBD single and free torque app does similar. Don’t know why, but whatever it’s displaying is not litres/100km. Can’t remember exact numbers, but probably in the 30s displayed while the amount of fuel out in the tank vs kms on the odometer is about 10l/100km.

Time to fill the tank, record the kms and get a calculator out. Do this for several tank fills to get an average.

 

[dantheman85]

I’ve just finish doing that and I got an average of 14.6l/100kms over 5 tanks. Mainly highway driving. 265/75r16 tyres.
sound about right?

 

[joe2006]

14.6 is high but really hard to compare. Mine is also on 265/75/16:s and with a gentle foot, will get under 10lph on relatively flat open road at 100kph with very few towns and slowing down. 80kph is the most economical speed and consumption continues to increase from there.
You calculated manually but have you checked that your odometer is correct?
An auto will use more fuel as well.
I remember the consensus quite a few years ago, that for some reason, the king cabs (Thai) used the most fuel.
If it makes you feel any better, I almost got to 30lph towing our van in a stiff wind between Winton and Hughenden and struggled to get to 80kph It has now been retired from towing anything but the 6x4 trailer.

 

[Old.Tony]

So this is a screen shot of my average fuel consumption after doing some ‘city driving’

what’s going on here?

The screen shot doesn't look completely right. The car shouldn't use 4L per hour when idling, it should be down between 1.7 and 2L, so it's possible that it's indicating 2x the usage.

 

[NavaraNavara]

The best I got is 13.6
We have a tough roads and I am careless driver

Mine is 3.0 auto 2012stx

 

[dantheman85]

The screen shot doesn't look completely right. The car shouldn't use 4L per hour when idling, it should be down between 1.7 and 2L, so it's possible that it's indicating 2x the usage.

So what would be the issue then?

 

[GunMentalGrey]

So what would be the issue then?

Something wrong with the way it’s either reading or displaying. It seem to be showing twice what the actual numbers are.

 

[Old.Tony]

The actual fuel flow rate is different to the amount injected (and there's a return line for fuel to go back to the tank). It might be using the flow rate (at idle, injector rail pressure is around 4,000psi).

It wouldn't be the first time that a piece of software made an incorrect calculation. Different ECUs report things in slightly different ways (because each manufacturer knows better than every other manufacturer, right?). Some software will actually allow you to make adjustments to the reported figures so that you get the right information displayed. For example, air pressure at sea level is about 14.7psi and some ECUs report a higher boost because this figure is added in, so you subtract 14.7 from the reported value to arrive at the actual boost pressure.

Because of things like this, software can't accurately work with every car - and the better software authors have configuration items to allow adjustments. Have a look in the config for yours and see if it has that feature. Ian Hawkin's "Torque" (one of the better tools I've found for real-time ECU data display) has numerous fields for adjusting incoming data.

 

[dantheman85]

Would a blocked dpf cause fuel consumption issues? I’m not getting any engine lights but could that be an issue?

 

[Old.Tony]

Yes. If the vehicle is trying to do a regen, it will pump extra fuel into the exhaust stroke so that the fuel lands on the DPF and ignites, burning off the soot. Several requires for this as you'd expect: reasonable vehicle speed (which means you're not in heavy traffic), engine above 1500rpm (so there's enough flow in the exhaust to encourage the burn).

Thing is, you'll spot it. Your car will produce plumes of greyish/whitish smoke (and I mean LOADS of smoke). The smoke will smell funny - it contains unburnt diesel. Don't breathe too much of it in!

Getting 550km to a tank isn't bad, if I still had a standard tank I'd probably be looking to refuel around then anyway. How much fuel are you putting in, after driving 550km? Do you record fuel purchased and km driven since last fill? Could you share some of those figures with us?