E46 325i on LPG, does this mpg drop sound right?
Discussion
Just yesterday picked up an E46 325i with a Romano LPG system. Brimmed it before setting off then did 202 miles on cruise control at 75mph indicated. Filled up with 37.4 litres on LPG upon getting home which I work out as 25mpg. Now obviously this equates to 50mpg in terms of cost, so I can't really complain, but I would've expected mid-30s mpg on a run like that. I know there's always some drop but should running LPG really give a 10mpg (30%) increase in fuel consumption?
I suppose my next step is to do a brim-to-brim calculation on petrol, but it seems like a bit of a waste of money when I could be running LPG!
One other thing. The pump where I brimmed up to begin with (BP at M180/M18 services) clicked itself off like a petrol pump. The one where I filled up at the end (Shell on M32) just slowed down to the point where the pennies where barely ticking up but didn't stop itself so I just gave up. There's a possibility the first pump clicked off with a lower level of gas than I filled up with at the second. Out of interest, do most pumps click themselves off or just slow down?
I suppose my next step is to do a brim-to-brim calculation on petrol, but it seems like a bit of a waste of money when I could be running LPG!
One other thing. The pump where I brimmed up to begin with (BP at M180/M18 services) clicked itself off like a petrol pump. The one where I filled up at the end (Shell on M32) just slowed down to the point where the pennies where barely ticking up but didn't stop itself so I just gave up. There's a possibility the first pump clicked off with a lower level of gas than I filled up with at the second. Out of interest, do most pumps click themselves off or just slow down?
It seems a bit low I'd expect to get a good 30's out of that run.
Re the pumps most pumps shut off when the tank reaches 80% capacity, if you find it creeping upits probably because the tank vent is venting the excess pressure/ volume. Once the fill starts getting really slow I'd just stop.
In Italy on attended sites they would keep filling until you could hear the safety valve chattering away as the more they put in, even though its gassing off, the more they sell.
Cheers,
Tony
Re the pumps most pumps shut off when the tank reaches 80% capacity, if you find it creeping upits probably because the tank vent is venting the excess pressure/ volume. Once the fill starts getting really slow I'd just stop.
In Italy on attended sites they would keep filling until you could hear the safety valve chattering away as the more they put in, even though its gassing off, the more they sell.
Cheers,
Tony
That does sound fairly low. I got 22 the other week in a long run with my LPG E39 540 and wasn't using cruise control or hanging about.
Could be worth getting your O2 sensors checked, also if you've got an OBD reader scan the car for any existing faults too, mine had a bad camshaft sensor and it made a huge difference to performance and economy once replaced.
Could be worth getting your O2 sensors checked, also if you've got an OBD reader scan the car for any existing faults too, mine had a bad camshaft sensor and it made a huge difference to performance and economy once replaced.
Synchromesh said:
Just yesterday picked up an E46 325i with a Romano LPG system. Brimmed it before setting off then did 202 miles on cruise control at 75mph indicated. Filled up with 37.4 litres on LPG upon getting home which I work out as 25mpg. Now obviously this equates to 50mpg in terms of cost, so I can't really complain, but I would've expected mid-30s mpg on a run like that. I know there's always some drop but should running LPG really give a 10mpg (30%) increase in fuel consumption?
I suppose my next step is to do a brim-to-brim calculation on petrol, but it seems like a bit of a waste of money when I could be running LPG!
One other thing. The pump where I brimmed up to begin with (BP at M180/M18 services) clicked itself off like a petrol pump. The one where I filled up at the end (Shell on M32) just slowed down to the point where the pennies where barely ticking up but didn't stop itself so I just gave up. There's a possibility the first pump clicked off with a lower level of gas than I filled up with at the second. Out of interest, do most pumps click themselves off or just slow down?
Fuel ecconomy can be 15-20% worse on LPG owing to the lower enrgy density of the fuel. You don't notice any power drop because the ECU puts more fuel in to maintain the same torque at a given RPM. What would be normal (real life, not manufacturer's EU cycle figure) for this car on petrol? My 225bhp Impreza has returned 24.53mpg over the last 17,000 miles because I am sad enough to have measured it.I suppose my next step is to do a brim-to-brim calculation on petrol, but it seems like a bit of a waste of money when I could be running LPG!
One other thing. The pump where I brimmed up to begin with (BP at M180/M18 services) clicked itself off like a petrol pump. The one where I filled up at the end (Shell on M32) just slowed down to the point where the pennies where barely ticking up but didn't stop itself so I just gave up. There's a possibility the first pump clicked off with a lower level of gas than I filled up with at the second. Out of interest, do most pumps click themselves off or just slow down?
Some pumps slow down others just pump till they cavitate and auto-stop. You only get about 80% off the nominal capacity in the tank because it is sealed and the more liquid you put in, the more you compress the gas. The best I've got in my 50l tank is 42l; it depends on the small variations in delivery pressure at the pump.
Get yourself logged on to www.filllpg.co.uk for LPG locations and prices. IIRC Asda Cribbs Causeway is the cheapest LPG in Bristol.
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