On board trip computer- fuel economy

[Moto Mech]

I dont have one and would most likely cry if  I did but the question-
The standard indash fuel economy read outs found in most late model vehicles, are they telling you what you want to see or are they accurate? Do people actually back up the read out at the bowser or just take the reading as gospel?
A few people I know have these in late model 4c diesel utes and are always bragging about fuel economy as low as 6-7lt/100kms but never tell me the actual bowser usage. And as a few of these are coming away next year on a double simpson desert crossing with me, I need to find out true economy.
Cheers Nick

[MDS69]

On the Triton forum there are guys claiming 8-9's per 100 for a 4WD some with accessories fitted but I think they are quoting onboard trip computer. I have a 2WD Triton with no accessories and can't get below 10L/100 bowser/fuelly.com calculated.

Edit-
I just had another think about and maybe the 4WD's I mentioned are manual with highway trips and mine is an auto with mostly city driving, who knows.

[maurerless]

My 2010 D-Max has an instant and an Average fuel calculation.

When doing a calculation on kilometers v. liters, it came out similar to the average of 8.5. (Edit - as claimed by the computer)

Problem is though the speedo is usually showing speed slightly slower than the GPS. I'm guessing it also clocks the kilometers slightly less than actual (by up to 4km per 100km). So, even though I have good idea of the actual liters of diesel I've bought, I don't have an accurate idea of the kilometers traveled.

What I'm not sure of is how much extra I use when towing, but I think it's only up around 10l/100k.

Tony

[RebsWA]

I've had 2 SR5 D4D Hilux's with onboard computers so can only speak for them.
Both got the 29" stock tyres replaced with 31"tyres from new. This made the speedo pretty much dead accurate compared with my (2) GPS's.
As for fuel, the  average economy reading was pretty damn accurate too. A quick calculation of litres she would take at the bowser and it was usually within a litre or two at the most. Pretty good I reckon and no point in fudging the figures cos you are only fooling yourself.
Won't quote any consumption figures as they vary with the type of driving, what you are towing etc. but suffice to say 9l/100km was about the best I achieved over several 150km trips on flat highway with no load or wind.
Ironically, the earlier one was a lot better than the later one  even though the official fuel consumption figures showed it the other way round.

 

[Estelle]

Too many variables when calculating fuel economy.

Just about given up on fuel economy.

Know your fuel gauge. Ours is 'better' down to half tank level, then seems to use fuel quickly.

On a trip, are there many hills? Going up an escarpment can use heaps. Depends on the gear you use, when you hit the go button etc.

On our way home today from Kiama up Mt. Ousley, it was hard going revving between 2.5 and 3.0 K RPM at about 80Km/Hr, but on the road to Picton, you could hear it 'tick over' running at 90Km/Hr at 1600RPM (Diesel). Smooth as a baby's...

Not much you can do about it, just change air filters, service etc.
We roughly average about 15L/100Km when towing. Depending on.... Headwind, hillls...

[johnyd]

My Commodore VXII sedan (I know not a great camping car) has a prediction of how far the car will travel on the remaining fuel that is fairly accurate.

With a full tank it claims 820km and I can do anywhere from 750-850km depending on conditions, whatever the readout is I usually come within 20km of it as long as the driving conditions don't change.  It doesn't do a historical one like I think you are talking about though.

[Kit_e_kat9]

I do mine the old fashioned way ... using Excel!  I find around town I get 550K's per tank, but can get almost 700k's per tank highway driving only. 

We don't have much in the way of "flat" around here, so (example only) if I was hooting along the Nulla-boring, then I expect things would be better as long as the wind wasn't blowing and no road trains passed by and temps were optimal for testing. 

Even in identical vehicles fuel usage varies.  Learn what yours will do and live with it.  Keep records (I use the fuel dockets) and you can easily see if things go pear shaped for whatever reason. 

Kit_e

[bobnrob]

No on-board gizmo in ours, & I'm absolutely useless when it comes to maths, so I use a free program called MyCar Monitor

[Fivid]

I work the patrol out using actual distances and actual litres used according to the bowser reading.  I can occasionally get it down around 10 litres per 100Km, generally it uses around 12.5 litres per 100 and with the CT on the back uses slightly more if I drive at 90Km/h and heaps more, up to 16 litres / 100Km, if I sit on 110Km/h.

The work car computer tells me I average 14 litres / 100Km (varies between 13.9 and 14.1).  I drive an average of 75Km per day, mostly in a 100Km zone but have to put around 70 litres of fuel in every 5 days (around the 350 - 370 Km mark so it obviously uses lots more than 14 litres / 100Km.  Closer to 19 litres.  It is easily the most fuel thirsty car I have ever driven and it only has 6 cyl.

 
Dave