My 2004 L322 4.4 V8 has a Stag Lpg system with what I believe is an 84 litre tank. I've only owned it 2 weeks and on a full tank of gas I've just managed to get 150 miles out of it and it's empty ? That's driving to work, 10 miles each way 90% on the motorway. Does that seem right as I was expecting to get a lot more miles out of a full LPG tank ?

I should've mentioned the LPG system was serviced about 2000 miles/6 months ago. I've also noticed I don't have to touch the throttle very much and the LPG light flashes where it's switching over to petrol ?

Do you know how much actually goes into the tank ?? Normally there is the 80% limiter so iso 84 the actual amount going is is 67 liter. Doing 150 miles results in 3.63 km/liter and that is BAD. My big ass American GMC van, sized like a 20ft container did double that.

So yes, I'd say you have an issue. I'd suggest to take it to a good LPG installer and have it sorted. Hopefully it just needs readjustment BUT it could also be a leak in one of the fuel lines or elsewhere in the system (evaporator etc.). MY 2010 5.0 SC Galway green and sand interior!!
Have the Faultmate MSV2 Extreme to be tinkering with the settings etc. !!

I've got 2 tanks fitted giving 180lt in total. This gives me between 480 and 550 miles depending on journey or if I've got a heavy right foot.
So I'd agree, looks like you have a problem somewhere. 2012 Westminster 4.4 TDV8

Si, I have the same system as you. I get 220-240 on a tank using c. 75 ltrs. The tank holds up to 85/90 but you can normally only get up to 75 in one refill. Cost per mile should be 18-20pence per mile.

If I were you I would take it to professautogas (http://professautogas.co.uk/) over in wales. They are stag specialist installers and service agents and are very good. They will set the parameters correctly and service it. I reckon your filters are gubbed and need changing.

Feel free to contact me ref any of this.

Last edited by Dolphinboy on 14th Jun 2017 8:55pm. Edited 1 time in total

I have a 4.2 SC and get between 173 and 184 out of 78 Litres and this has been the norm ever since it has been fitted the car tells me i am doing 14.5 MPG the car has done over 40,000miles on LPG and i am more than happy with the fuel consumption, dont know about normally aspirated 4.4 but what does the car say?

Mine has a small tank which is a bit annoying but £30 gets me 180 miles roughly

I get between 200 and 250 on 72 litres, depending on where and how fast I'm driving.

So I've been told that when the red light is on on the lpg display that in fact it isn't empty so I carried on using it over the weekend and got to 190 miles and it still didn't run out. I filled the tank back up yesterday so will now let it run until it's completely empty and switches back to petrol and see how many miles that gets me.

On my car, the red light means about 1/4 tank left. If I drive it till empty, it suddenly loses power, but idles. I then switch it back, but only as I try and sometimes wring out the last drop! I wouldn't want to do this in heavy traffic mind you.
On my old rangie, it would buzz a sounder, and auto flick to petrol. I have a 95 litre tank I get maybe 200 on a run. You should really calculate the pence per mile, as your accurate gauge. Plan your journeys with available distant lpg stations, and keep the petrol tank half empty.

200-220 miles on 67-68 litres here

220-235 on 68-72l for me. Current:
- 2017 L405 3.0 V6 Autobiography
Sold:
- 2013 L405 4.4 TDV8 Vogue
- 2004 L322 4.4 Vogue (BRC LPG)
- 2002 L322 4.4 HSE (having fixed timing chain guides)
- 2000 P38 4.6 Vogue (BRC LPG)
- 1981 2-door In-Vogue
- 1980 Ex-Army SIII LWB
- 1976 SIII LWB
- 1968 SIIA
Stripped for parts:
- 2003 L322 4.4 Vogue

The fill lights on the changeover switch are an estimation and not precise measurement. The installer goes by his experience. Reset your trip mileage every time you fill up. As an estimation you should get 200 miles to a tank.
Accelerating hard up hill when your around the 150 mark may cut the lpg off and it will change back to petrol. When on the flat change back to gas. It may take a few goes to get the air gaps out the gas pipe to the vapouriser.
If you are adventurous buy a OBD scanner. This will show your fuel trims for each bank in the form of short term and long term. Shorts should be around the zero mark and long around 4-5%. Scanners can be purchased for as little as £15 and can have the benefit of clearing codes without going to main stealers. On that note always check why a code has popped up