Petrol - How much do you use per annum

[scottyf]

Lets say all your LPG needs are being meet. Your system works well etc.

This question is quite well open depending on your system and how it works.
I use a multipoint system that changes over when the reducer hits a temp of 25 degrees. Any lower and it struggles.


I'm finding that during the last couple of months I probably stick a tenner or just over 8 Litres to every 700-1000 miles on LPG.

So generally that means each year if I went off these figures I'd need to stick in about £220 worth of petrol a year for roughly 18'000 miles.

I'm quite surprised by this as it does eat into those LPG savings.

[Brian_H]

Really depends on your driving habits - if you longer distances then it sounds like a lot, if you do lots of short trips where lots of time is spent warming up before switchover (or it doesn't even get chance to switchover) then probabbly not.

Might help if you gave a clue what vehicle your using as well? The anwser will differ obviously for a corsa vs a v8 range rover.

The factory fit i have (when it was working, which it currently isn't) had fuel in the tank for over a year with only around a quarter of the tank used (some when it had run out of gas to go and refuel - i have had it full of petrol on the gauge for months on end before). The multipoint sequential system i had uses more petrol, but it depends on temperature to some degree, even that i don't usually use more than around 5l over a typical week unless its run out (the gauge on that one isn't so helpful as it only starts reading less than full when its got less than around 1/4 of the contents left in which time i'm not always passing a filling station before it runs out).

Most of my journeys are around 75 mile mark though

[DodgeRover]

Managed over a year on the original tank of petrol with my factory fit vauxhall combo, it used to run on petrol for about 40 seconds from cold on a warm day and drive 200 yards before switching over on the coldest.

[scottyf]

I know it will matter what system car and settings.

But I feel I am using up a lot more petrol than I first anticipated. My commute is 25 miles each way.
I think I feel like I am using a lot more petrol than I first thought. But then again its becomeing winter so I imagine in summer I will hardly use any...


At the current rate though it works out close to 12p per mile. I was doing 16-17p a mile on petrol.
Given the lower rate of petrol at the moment I reckon that the gap has clsoed between the two.

Still it'll be interesting to see how it performs over summer.

[Brian_H]

It does sound a little high to me, although at the moment the gas prices are varying somewhat depending where you are which will effect your calculations (and whilst they have generally fallen they haven't fallen as much as petrol yet).

How long does your car take to warm up to switching over temp? (25 degrees isn't particually high so wouldn't expect it to take long - also note if you leave it to run whilst warming up that you usually won't see it change till you acclerate/decelerate depending how its setup). Mine generally takes around 2 miles at the moment, longer if its colder as you say (but its got a min temp of 40 degrees) which takes me around 4 minutes from home to switchover.

Some systems (you haven't mentioned which you have) can also be set to wait a specified number of seconds from starting before switching as well which has more of an effect on short drives.

[scottyf]

LPGtech System.

I can change the settings and start on gas if I like. But I tend not too.
It takes less than a mile generally even in this weather. I've only recently dropped it to that level before it was 35 degrees.

The above shocks me though that some people have managed to last a complete year before adding petrol. I'll be lucky to do two complete weeks before topping up a tenner in petrol...

Maybe i'll try tweaking some settings see what I can do.

[kbs]

LPGtech System.

I can change the settings and start on gas if I like. But I tend not too.
It takes less than a mile generally even in this weather. I've only recently dropped it to that level before it was 35 degrees.

The above shocks me though that some people have managed to last a complete year before adding petrol. I'll be lucky to do two complete weeks before topping up a tenner in petrol...

Maybe i'll try tweaking some settings see what I can do.

If this is a multipoint injection system where the petrol injectors are interrupted by the LPG system and the Petrol (fuel rail) pressure is maintained whilst on gas.......

Is it possible that you have one (or more) petrol injectors dribbling when they are not being pulsed by the ECU?
Is it possible that your LPG ECU is not disabling (all) of the petrol injectors whilst running on LPG?
Either way the engine would be running on LPG and Petrol which is the only way my limited mind can imagine using that much Petrol when you only drive two miles a day on it (unless its leaking or you have a nephew/neice with a moped and a hose).

[scottyf]

If this is a multipoint injection system where the petrol injectors are interrupted by the LPG system and the Petrol (fuel rail) pressure is maintained whilst on gas.......

Yes multipoint system

Is it possible that you have one (or more) petrol injectors dribbling when they are not being pulsed by the ECU?

I did think this that maybe that was happening...

Is it possible that your LPG ECU is not disabling (all) of the petrol injectors whilst running on LPG?

Its definitely disabling the Injectors and all of them at that. I've double checked.

Either way the engine would be running on LPG and Petrol which is the only way my limited mind can imagine using that much Petrol when you only drive two miles a day on it (unless its leaking or you have a nephew/neice with a moped and a hose).

Potentially... This was my thoughts. I know that on cold i'd be lucky to get 10-15mpg. Given that I only fill up with a tenner petrol which is just over 8 Litres or less than two gallon I would have thought it might last me for than say ten days... Might be wrong though...

[Brian_H]

the other thing worth being aware of is that some cars don't use the fuel sender in the tank to directly feed the level shown on the gauge - instead they take a reading when starting and calculate from the fuel pressue and injector times what fuel is left and display that (fine under normal circumstances but noticable in this state since your not actually using the fuel).

How are you telling the amount used? most reliable way is to fill the tank then measure how much its used once you've done a week or so.

[scottyf]

The guage on the petrol does go diwn albeit slowly when on gas. It would be interesting to know that id almost be at a full tank given the anount of fuel fill ups. But I diubt that. Id feel it in the weight of the car and how it drives.

Im just putting a tenner in when ut reaches its reserve which is about a gallon and a bit.

[Brian_H]

Give a clue what vehicle your using someone might be able to confirm the gauge and if it does that normally. It should reset on refilling/stopping anyway so may not be that, just thinking it may be your thinking its empty when its not really as empty as it suggests.

The problem with that setup is if i start the car when its parked on a hill the gauge reads wrong for some time after starting and isn't clever enough to correct the reading to somewhere near accurate (over a quarter of a tank can indicate empty on mine if parted on my mates driveway).

Best way as said to get an accurate/measurable reading is to fill the tank and see how much it takes at a refill. Could be a leaky injector though as you'd never notice it when running on petrol.

[scottyf]

Yeah might well be a leaky injector that is not fully closing.
Thing is I would then have to find said leaky injector. I have a set of four I could swap over. Given they are petrol injectors I could wiggle them out fairly easily.

Thing is its probably not worth the hassle. Just means one cylinder is getting a little bit of gas and petrol.

The Car is an Alfa 147. The gauge has always been fairly accurate. Ie if I booted it on petrol it would show to change how long it would last. Same with range. You can tell it changes. I believe it drops down a little while driving on gas to show its using something. But then when I am back in the car and start it up it resets its self.

Same as when I refuel petrol.

Again though these are very small issues and to be honest I come from a world of motorbikes where by a fuel gauge never really existed. I always went off mileage. Since the LPG tank fuel sender isn't that accurate (Far more now that I tweaked it) but still there's only four lights (100,75,50,25) and one red to indicate empty.

Strange. Wouldn't be that surprised if I did have a slightly leaky injector. Can the system use both at the same time at all?

[Gilbertd]

Wouldn't be that surprised if I did have a slightly leaky injector. Can the system use both at the same time at all?

Yes, but the lambda sensor will pick up the rich mixture from one cylinder and cause the petrol ECU to adjust the fuel trims to make it leaner and get it correct again. Problem is that it will be looking at an average of all 4 cylinders so you'll have one still running a bit rich and the other 3 all running lean.

[scottyf]

Had a quick look tonight. All appears fine. Tested injectors. Again all fine.
Meh just seems my car likes to use a bit on start up.

[Gilbertd]

You are going to be using petrol at a time when it uses the most. So if you would expect it to do 30 mpg overall, then it's probably doing less than 10 mpg when first started from stone cold. That's the only time it's going to be running on petrol now unfortunately.....

[scottyf]

Yeah just seems that way. Played around with a few settings to get the switchover to happen a bit sooner. Its been far quicker these few mild mornings and its hardly using any petrol.

Although played with the map a bit more and I may have just leaned it out a bit too far for a motorway journey. Will revisit it again tonight.

Must admit I'm having quite a bit of fun playing with all the settings. I wish I could get software like this that I could play around with the cars original map settings. Would be more intriguing to play with those too!

[Zebedee]

I put maybe £20 of petrol in a year.
Mine starts on gas and is only ever switched over to petrol once a month to make sure everything still works.

[3sGTE]

Sounds about right to me. I average 2 starts a day, and probably a tankful of petrol a year, including short periods when I run out of gas etc.

Worth bearing in mind that leaning it out will have no impact on a motorway cruise as the petrol ecu will just be compensating more to maintain a lambda of 1. All it will do is throw your cars mpg gauge further out when on lpg.

[scottyf]

Its okay I played with some of the settings and I do about 1000miles to a tenner of petrol.
So I won't complain too much for now.

I am sure I could start it on gas if I wanted. But I don't think its too much to ask for at the moment.