LPG Ancillary Costs (Flashlube and start-up petrol)

[Jamp]

Hi All,

I am calculating the break-even point for an LPG installation on my vehicle. I know I would need flashlube injection and an allowance for starting on petrol. Can anyone give me an idea of what these supplementary costs amount to, on a per mile basis. ie. petrol is currently £1.32/L, LPG is £0.66/L, but I also need to factor in an amount per mile for allowance for starting petrol and flashlube, in order to make a fair comparison. My commute is quite short at 8 miles each way, so for that I guess my proportional petrol usage is going to be relatively high. I know the Flashlube is expensive but how many miles does it last (on a Subaru that needs the valve seat protection)?

Cheers,

Jamp

[mat_fenwick]

Dunno about Flashlube, and calculating petrol usage is going to be very difficult as there's so many variables! Ambient temperature (garaged/time of year), what the changeover temperature is set to, how you drive it from a cold start (also uphill/downhill/traffic). I'd say work on the very rough basis of a mile, but you'll be using proportionally more petrol as it's during the warm up phase. Something like a Kenlowe Hotstart might really pay for itself in your situation if you can switch onto gas instantly…

[rossko]

Recommended Flashlube dose is 1ml per litre of fuel, so that should be easy to cost.

To estimate petrol, I would cost the first 1.5 mile usage. In reality it'll be less than that - but that first half mile is the cold-running fuel-guzzling part.

[Jamp]

Thanks both. That's around £0.013 of Flashlube per litre of LPG then. The petrol consumption is going to do more harm to my figures. I'd guess from your guidance that I'm going to use roughly 1L of petrol to 9L of LPG. My regular commute makes up around half of my mileage, and other journeys are generally longer. The car is also garaged over-night so never has a very cold start-up, though the Kenlowe Hotstart, or a home made alternative, sound very interesting. I will therefore be paying £0.066 extra per L of LPG, to cover the extra cost of petrol. So to answer my original question, it looks like around 8p for ancillaries, per L of LPG, for my circumstances.

[classicswede]

The hotstart is a good idea and would give you instant switch over, reduced engine wear and instant heater

[mat_fenwick]

To me they don't make sense in financial terms to spend £300 odd on a normal car unless you're keeping it a very long time. But if it means cheap fuel 30 seconds from startup, assuming you have access to mains power at work, then it becomes a lot more justifiable! If/when I get an everyday driver LPG car (also hopefully a Subaru) then I will be fitting one.

[classicswede]

There are cheaper alternatives available.

Not for as I could not be bothered plugging it in all the time but if you can and the car is a keeper then it is well worth it.

[bxman]

Hi
If you were to use a mixer system you can virtually eliminate petrol costs
With the temp sensor disconnected I am on lpg within 2 seconds of start up from cold summer and winter.
with no flashlube but that is on a 15 year old PSA engine.
good luck with your project
cheers Patrick

[Gilbertd]

I would have said the same but I don't think a single point would be a good idea on a Scooby. Being a flat engine it's going to have a pretty large inlet manifold ready to go bang when the time comes and I suspect it's going to be made of plastic too. One slight hiccup is going to get very expensive, far more than using the odd bit of petrol.

[billynoband]

Depending on what lpg system you have it's possible to start on lpg in warm weather. Disadvantage is the lpg injectors will not last as long, if you don't mind replacing them yourself and can do any job on a car this can save money in the long run. You also have the chance that if you start on lpg when too cold all the time then the car may play up slightly,stuttering untill warm then the cars petrol ecu will try to compensate and you may get the engine check light come on and the tuning will go all over the place. If you run a banger and like to play with cars this is not a problem but with a nice car it's probably not worth it as not all cars petrol ecu will reset easily like my vx and mitsubishi.
Flashlube wise, my wifes jap car uses very little,only 4 or 5 drops a minute so very cheap. If I use the recommended dose then the engine light comes on. All cars are different though, you may or may not find this. Let your supplier advise you, our old vauxhall and mitsubishi are ok to experiment on,a nice car is not.

[Tubbs]

Its interesting you should say that about a flashlube putting the light on. Recently fitted an electronic one on a turbo. Set at the right position. Returned with a missfire. Turned the flashlube from 5 to 3 and it went away....

[Clifford Pope]

I have a basic mixer system, and although it is true it will run on LPG from start-up, it runs very badly until it has warmed up, especially in cold weather. So I always start on petrol and switch over after a mile or so, depending on the temperature.

But as most engine wear occurs in the early moments after start-up, I realise that is probably throwing away one of the major advantages of LPG. Certainly I don't notice the fabled clean oil, even though it runs 99% of the time on LPG. Those early minutes appear to be crucial.

[Gilbertd]

I have a basic mixer system, and although it is true it will run on LPG from start-up, it runs very badly until it has warmed up, especially in cold weather.

What car is it, as all of mine have always run perfectly from cold on LPG. In fact, the LSE is set to start on LPG so it never uses any petrol at all.

[classicswede]

Volvo 240 Bosch L jet with GMS mixer system fitted.


I start all my mixer cars on LPG and many of them no longer even have petrol tanks fitted!