Fuel Usage Comparison

[Wally]

Has there been a thread on instantaneous fuel consumption amongst the members' different cars with trip computer?

I would be interested to know what the figures are for say:

constant 60kph on a flat stretch
and 100kph.

I'm happy to post my 6.0 litre figures over the weekend as a baseline.

[aquahead2001]

This is a meaningless comparison, only average economy over a set distance and with set parameters really can be compared. Instant fuel usage is just like those ridiculous vacuum economy gauges from the 80's, put your foot down to accelerate and loose vacuum and thus use more fuel. No worries, for a small period of the drive, you had to accelerate, big deal. But then you had to decelerate or coast, or maintain speed. It’s not just one part of the drive that impacts on fuel usage, it’s all the drive.

How much fuel did you use over the journey is what you really want to know.

[Hunter]

LOL my old Gemini had one of those 'economy' gauges. I would have rather had a tacho.

Instant fuel usage is pointless btw.

[EDManual]

I think its a very good comparison of aerodynamics and low engine rev efficiancy. Sure do it for at least20 km or so though of the same conditions. Preferable a full tank of same conditions and fill up on the exact same angle at the servo.

I have an ED Falcon manual, not using the instant but full tanks on flat country roads. All crusing.

90 km/h 7.5l/100
100km/h 8l/100
120 9l
140 12
160 14

With a car trailer that weighs 1100kg at 110-120 10L/100 Made it from Geelong to Victor harbour on 1 tank!!
With a car trailer and a 1100kg car on top on the way back at 110 to 120 12.5l/100!! Fantastic I thought!!
With a single axle cage trailer and a motorbike at 110 to 120ish 14l/100! Bah. Thats wind resistance for you.

I really struggle to go under 110 on any main road so found doing 100 or 90 just painful! Speedo is very accurate, so the GPS says. Run taller tyres and it makes up for the built in error of 95 actual 100 indicated.

[Wally]

Originally Posted by aquahead2001

This is a meaningless comparison, only average economy over a set distance and with set parameters really can be compared. Instant fuel usage is just like those ridiculous vacuum economy gauges from the 80's, put your foot down to accelerate and loose vacuum and thus use more fuel. No worries, for a small period of the drive, you had to accelerate, big deal. But then you had to decelerate or coast, or maintain speed. It’s not just one part of the drive that impacts on fuel usage, it’s all the drive.

How much fuel did you use over the journey is what you really want to know.

Well you may be right, but then agan you may be wrong. As I understand it, those figures that are bandied about for new cars are based on almost laboratory tests with the urban cycle taking only 195 seconds and the highway cycle 400 seconds.

So how would a real life instantaneous figure based on constant speed over the flat be any less relevant? Those "ridiculous" vacuum gauges did hold steady at consant speed and obviously the car makers don't think the instantaneous readout is all that ridiculous either.

Perhaps my wording was confusing. I meant to say :

constant 60kph on a flat stretch
and 100kph.

[Dauphin]

Using a long average:

AUII VCT Fairlane
16.0L/100km at 60 km/h - around town

7.5L/100km at 100 km/h - freeway

I can't seem to get it below 16L around town. Been trying for weeks. Going on the odometer, I get about 430 kms per 68L tank around town only.

This is with a 3100 hi-stall torque converter.

[MoreHPformyXR6]

Originally Posted by Wally

Has there been a thread on instantaneous fuel consumption amongst the members' different cars with trip computer?

I would be interested to know what the figures are for say:

constant 60kph on a flat stretch
and 100kph.

I'm happy to post my 6.0 litre figures over the weekend as a baseline.

Got back Sunday after putting a bit over 3700km under her belt for the return trip. (Car has done a touch over 24000 km's now). With three adults and very full boot of luggage. I was happy with the results sitting on 115km/ph in 110km zones and 105km/ph in the 100km zones (which is probally 1km/ph above the posted limits as my BA is really doing 96km when speedo says 100km. I averaged 9.8l/100km overall .
The low for the trip was 9.4l/100km and (the high was 10.1/100km - which included some highway kay's and about 250 km's of running around and short trips when we where there). I thought when I fitted my pacemaker headers (4495's) and 3' metal cat & XR6T exhaust maybe that stuffed my 02 sensor as I get 15l/100km or a bit more more in the city - short trips and heaps of stop start stuff. But after that trip im certain my 02 sensor is all good otherwise I cant imagine I would have got that kind of economy.

The above gives you a bit of a guide. But I think you need to be a bit more specific in your post so as you can do a decent comparison. Its all good to say at 100km/ph on the flat but is that a 5km trip 25km trip or 200 plus km/trip etc?

[madmelon]

I rekon those instantaneous fuel readouts are great. When I'm bored I just challenge myself to see how low I can keep it. I managed to keep the jag flicking between 6 and 7 on dead flat at 60km/h for about half a kay (Tom Ugly's bridge in Syd) when I still had it. I remember doing it at 100 and 110, but can't remember the numbers. Average for town was 14-16 depending on the week but that's what you get with a car that heavy.

[GORDZ]

accelerating i use 99L/100k's, cruising at 60kph I use 4.8, 80k's = 7L/100, 100k's = 8.9L/100ks 180k's (ute limiter)= 23L/100k's

[GORDZ]

but thats on a race track of course! ;)

[Bossxr8]

Instant fuel economy readings are always inaccurate, so don't take them as gospel cause doing it the old way of dividing how many litres it took to fill by the amount of kms travelled always brings a different result, and some cars can be way off.

[prydey]

comprehension skill are rather lacking i feel.

the OP isn't wanting to know what your car's ave economy is or how many km's you get from a tank or whatever.

on a flat stretch in my ba @ 60 its on about 7 and @ 100 its also on about 7.

i use cruise as well so that there is constant throttle % otherwise it could drop down even lower if you are coasting with close to zero throttle %.

In case you are wondering i didn't go out and do these tests after reading the thread. i just happened to be doing it one day on my way to work trying to see if there was much difference between leaving it in drive or flicking it over into sss mode and forcing it to lock up in 4th.

instantaneous does read marginally better if i force it to lock up in 4th but hardly enough to worry about.

[EDManual]

I find it funny that the Smart for2 does 8 to 9 litres per 100 at 110km/h!! Thats worse than new falcons! Even turbos!

[Wally]

My Calais with 6.0 engine is 7.8 @100 kph measured today over 1km.