Poor 'MPG' when using LPG
Discussion
I have just bought a car with a BRC LPG system. The car is registered as an alternative fuel car.
From my first run on LPG it looks like i am only managing to get about 20mpg, while on petrol i can average about 35 . Pretty much driving like an old lady on both tests, mixture of A and B roads.
Assuming this is way below what i should be getting, is there something I can troubleshoot this?
From my first run on LPG it looks like i am only managing to get about 20mpg, while on petrol i can average about 35 . Pretty much driving like an old lady on both tests, mixture of A and B roads.
Assuming this is way below what i should be getting, is there something I can troubleshoot this?
I wrote this post and then did some more sums and i am confused. I like to work in MPG but that is not as easy as it used to be..
My sums were somehow wrong though!
The car is a 2010 Subaru Outback 2.5 petrol.
I filled up with LPG and then 75 miles later i filled up again./
That was 17 litres @ 68p which worked out to £11.60
So. £11.60 to go 75 miles.
Two gallons of real petrol would be about £10 and would get me about the same distance in perfect driving conditions.
I cant really see any savings at all!
My sums were somehow wrong though!
The car is a 2010 Subaru Outback 2.5 petrol.
I filled up with LPG and then 75 miles later i filled up again./
That was 17 litres @ 68p which worked out to £11.60
So. £11.60 to go 75 miles.
Two gallons of real petrol would be about £10 and would get me about the same distance in perfect driving conditions.
I cant really see any savings at all!
Krikkit said:
LPG only has ~58% of the energy density per litre compared to petrol, so it's no surprise you've got "poor" MPG. What you've actually got is normal MPG.
35MPG > 20MPG isn't right - it should be about 80% of the petrol figure. OP - it needs looking at - If an electronic system it will likely need calibration as it's drifted off spec with time.Shuvi McTupya said:
I wrote this post and then did some more sums and i am confused. I like to work in MPG but that is not as easy as it used to be..
My sums were somehow wrong though!
The car is a 2010 Subaru Outback 2.5 petrol.
I filled up with LPG and then 75 miles later i filled up again./
That was 17 litres @ 68p which worked out to £11.60
So. £11.60 to go 75 miles.
Two gallons of real petrol would be about £10 and would get me about the same distance in perfect driving conditions.
I cant really see any savings at all!
I think you need to work it out properly My sums were somehow wrong though!
The car is a 2010 Subaru Outback 2.5 petrol.
I filled up with LPG and then 75 miles later i filled up again./
That was 17 litres @ 68p which worked out to £11.60
So. £11.60 to go 75 miles.
Two gallons of real petrol would be about £10 and would get me about the same distance in perfect driving conditions.
I cant really see any savings at all!
The savings from LPG shouldn't be debatable - they are facts.
DaveCWK said:
I think you need to work it out properly
The savings from LPG shouldn't be debatable - they are facts.
I am trying to work it out properly, but i seem to be coming up short The savings from LPG shouldn't be debatable - they are facts.
Once i filled the LPG tank, i made the return journey on petrol and averaged 35MPG
It seems to me that LPG is the same price per mile as Petrol (give or take).
Shuvi McTupya said:
I wrote this post and then did some more sums and i am confused. I like to work in MPG but that is not as easy as it used to be..
My sums were somehow wrong though!
The car is a 2010 Subaru Outback 2.5 petrol.
I filled up with LPG and then 75 miles later i filled up again./
That was 17 litres @ 68p which worked out to £11.60
So. £11.60 to go 75 miles.
Two gallons of real petrol would be about £10 and would get me about the same distance in perfect driving conditions.
I cant really see any savings at all!
Dont forget petrol is much cheaper at the moment, so 68P V ~£1.04.My sums were somehow wrong though!
The car is a 2010 Subaru Outback 2.5 petrol.
I filled up with LPG and then 75 miles later i filled up again./
That was 17 litres @ 68p which worked out to £11.60
So. £11.60 to go 75 miles.
Two gallons of real petrol would be about £10 and would get me about the same distance in perfect driving conditions.
I cant really see any savings at all!
Where LPG is normally around 20% worse off, i doubt there is much savings.
When petrol is back near £1.30, there will be a bigger saving.
V8 Stang said:
Dont forget petrol is much cheaper at the moment, so 68P V ~£1.04.
Where LPG is normally around 20% worse off, i doubt there is much savings.
When petrol is back near £1.30, there will be a bigger saving.
This is true..Where LPG is normally around 20% worse off, i doubt there is much savings.
When petrol is back near £1.30, there will be a bigger saving.
I guess at them moment it isnt really worth me going out of my way to find LPG!
It sounds as if the system isn’t set up properly, you should be getting nearer to 80% of the actual MPG on gas that you do on petrol. If it does 35mpg on petrol, you really shouldn’t see less than about 30mpg on gas (actual fuel used).
I run my Jeep on a Prinz system and it does 20mpg on petrol (on a run) and about 17-18 on lpg. Cost-wise of course it’s a result, even with cheap petrol.
I run my Jeep on a Prinz system and it does 20mpg on petrol (on a run) and about 17-18 on lpg. Cost-wise of course it’s a result, even with cheap petrol.
Edited by Chris-S on Sunday 28th June 20:32
I will continue my testing.
The figures may also have been thrown off a little in the first test as when I picked up the car, the tyre pressures were very low. I wasn't able to tell by looking at them, but the rears were at 18PSI and one of the fronts wasnt much better..
If that didnt affect the economy, atleast it seems to have improved the slight pull to the left.
ETA: Thanks to the mod that moved it here. i didnt know this place existed.
The figures may also have been thrown off a little in the first test as when I picked up the car, the tyre pressures were very low. I wasn't able to tell by looking at them, but the rears were at 18PSI and one of the fronts wasnt much better..
If that didnt affect the economy, atleast it seems to have improved the slight pull to the left.
ETA: Thanks to the mod that moved it here. i didnt know this place existed.
CDB1983 said:
It definitely sounds like there is an issue with your LPG installation, has it been checked for leaks? Injectors can fail and leak slightly as can the reducer. (Not an expensive fix)
I'm getting 10.3L /100kms on petrol and it goes to around 11l/100 Kms on LPG. (Out of a 4.3 V8)
I just bought it so I haven't taken it to anyone to look at yet. I'm getting 10.3L /100kms on petrol and it goes to around 11l/100 Kms on LPG. (Out of a 4.3 V8)
I will do a few more test runs first. The figures you are getting sound like what I was expecting to see.
Something is definitely off somewhere!
I just topped up again after 20 miles on LPG and it used just over 2 litres (topping up £1.20 was quite embarrassing)
Then i drove 40miles on petrol and brimmed the tank for £5.50.
Those figures show a huge saving on LPG so the testing is inconsistent somehow!
I just topped up again after 20 miles on LPG and it used just over 2 litres (topping up £1.20 was quite embarrassing)
Then i drove 40miles on petrol and brimmed the tank for £5.50.
Those figures show a huge saving on LPG so the testing is inconsistent somehow!
My guess in that scenario is a very slow leak letting fuel out when the car is parked. I had LPG issues twice as mentioned above. Once was the diaphragm on the reducer. Usually at the back of the engine bay and once with injectors. They are generally pretty robust systems though. Did you get a little folder for the lpg system? If the injectors are Barracuda then there's a very high chance the fault is with them.
CDB1983 said:
My guess in that scenario is a very slow leak letting fuel out when the car is parked. I had LPG issues twice as mentioned above. Once was the diaphragm on the reducer. Usually at the back of the engine bay and once with injectors. They are generally pretty robust systems though. Did you get a little folder for the lpg system? If the injectors are Barracuda then there's a very high chance the fault is with them.
Yes i have a book for the LPG system. It looks like it was supplied by an outfit in Poland and fitted by an authorised installer in Stoke on Trent in 2016.The Injector type does not seem to be listed in the info I have. It does list :
valve type: Tomasetto
reducer type: 1500
system type : 32?
Are the documents in polish? Upload them here or pm me them and I'll ask my wife to decifer what you have . We are taking her Volvo for an LPG service (in Poland) next week so will ask them what they think. I'm guessing if it's a polish made system it will have an lpgtech ECU. The reducers (reduktor) on Polish could be anything, post pictures and I'll ask the guys that look after ours for advice on what you should be having checked out.
. We are taking her Volvo for an LPG service (in Poland) next week so will ask them what they think. I'm guessing if it's a polish made system it will have an lpgtech ECU. The reducers (reduktor) on Polish could be anything, post pictures and I'll ask the guys that look after ours for advice on what you should be having checked out. This is the reducer
In situ
If you can find any little modules such as this then that will help you decifer what you have
I'm on my second reducer (reduktor) on around 90k miles and second set of injectors.
Less than £150 for 8 injectors and the reduktor Is about 80 quid so not hugely expensive. Just annoying.
Do you have any starting issues?
In situ
If you can find any little modules such as this then that will help you decifer what you have
I'm on my second reducer (reduktor) on around 90k miles and second set of injectors.
Less than £150 for 8 injectors and the reduktor Is about 80 quid so not hugely expensive. Just annoying.
Do you have any starting issues?
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