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[Opomes]

Hello,

I am pondering over the fuel consumption of my 3.2 Omega auto. Currently I average ~22 imperial MPG (I'm not from the UK, the actual consumption read-out is ~12.8 L/100 km) at something like 25-26 mph (40-42 km/h) according to the on-board computer (OBC). Also about ~31.4 MPG (9L/100km) at ~62 mph (100 km/h) on 205/65R15 M+S tyres.
Since it is fitted with an LPG system, I'm interested in whether the OBC is measuring the consumption based on petrol or LPG figures (or does it measure the consumption based on oxygen flow?). The reason being, LPG has lower energy value per litre compared to petrol and ~20% more of it is required for the same energy output.

What consumption figures are you getting on your 3.2 Omega auto? Or on your LPG Omega or other cars (if the OBCs are similar). Does the OBC consumption value alter while changing between petrol and LPG)?

Best regards.

[Migv6 le Frog Fan]

My consumption is 23.5mpg from my 3.2 auto. Mostly  driven single carriageway type roads, so maybe not very representative ?

[zirk]

Your calculations are slightly out, probably US converter.

The calculate Euro to UK or the other way around use the common number 282 (or 282.4 if your really fussy) ie,-

12.8 L/100 km is 282 / 12.8 = 22mpg
or
22mpg is 282 / 22 = 12.8 L/100 km

 

[zirk]

The OBC can be a fair way out on LPG, normally reading a lot higher (in MPG) than the actual, only way real way is to do a brim to brim on LPG vs the millage over that period, then take into account the percentage of Petrol used (on Start Up) over short and long trips.

As a rough guide your consumption of LPG will be around 12 to 15% less on LPG over your Petrol consumption.

In my experience -

Petrol / LPG MPG
3.2 Auto, Short trips 21 / 18 mpg, Motorway 28 / 24 mpg
3.2 Manual, Short trips 25 / 22 mpg, Motorway 32 / 28 mpg

[TheBoy]

The onboard fuel computer will misread on LPG.  Next time I turn on my PC upstairs, I can post up my figures from near 7yrs of lpg on a 3.2

[tunnie]

Not LPG but my 3.2 averages 24mpg on my work commute, mixed motorway and heavy city traffic.

Longer runs I see low 30’s if I take it easy, say on an economical drive to Portsmouth

[Strangechap]

I get 20mpg on average on my 3.0.

Was 18mpg with my old whiney gearbox, but thankfully I broke that.

[TheBoy]

Not LPG but my 3.2 averages 24mpg on my work commute, mixed motorway and heavy city traffic.

Longer runs I see low 30’s if I take it easy, say on an economical drive to Portsmouth

But you are quite unique, mr tunnie




What *really* kills 3.2 mpg is urban, even with a light foot.  A combination of auto plus the way the ECU is mapped, I suspect.

[Nick W]

I get 20mpg on average on my 3.0.

Was 18mpg with my old whiney gearbox, but thankfully I broke that.

my 2mile commute has hammered my(3.0 auto estate) average down to 24mpg. With an occasional longer trip 300 miles from a tank is still just about possible. On a run, 400miles from a tankful isn't difficult.


When I start using it properly, I expect the 1.8 Metro to return mid 40s

[tunnie]

Not LPG but my 3.2 averages 24mpg on my work commute, mixed motorway and heavy city traffic.

Longer runs I see low 30’s if I take it easy, say on an economical drive to Portsmouth

But you are quite unique, mr tunnie




What *really* kills 3.2 mpg is urban, even with a light foot.  A combination of auto plus the way the ECU is mapped, I suspect.

Yup. Hence work run so rubbish on run to work. Lots of A4 traffic, stop start.

[Lazydocker]

Not LPG but my 3.2 averages 24mpg on my work commute, mixed motorway and heavy city traffic.

Longer runs I see low 30’s if I take it easy, say on an economical drive to Portsmouth

But you are quite unique, mr tunnie




What *really* kills 3.2 mpg is urban, even with a light foot.  A combination of auto plus the way the ECU is mapped, I suspect.

That’s one way to put it