Why???........
Saint: yep even taking into account say 15mpg in real terms compared to the 18mpg on the dash, I should be getting more miles than I am. Just noticed a bottle of valve cleaner fluid that is linked up to the log system in the engine bay. This is almost empty and looks more than a couple if years old. Do you know if this could have an effect on mpg and if I can just replace it myself? Lpg is all new to me but if the injectors are gunked up and possibly leaking this would lead to poorer effeciency just as dirty injectors in a petrol engine right? Seems to be loosing coolant too although on the last service it was noted a small leak from the t connection that splices into the coolant lines for the lpg system. I suppose this is probably the cause although I can't see it in the bay personally.
I do a good mix of town and motorway driving to work and back, I drive like a granny, rarely opening her up unless I have too...and I get 15.3mpg on LPG although this has dipped a tad recently to 15.12mpg...from my records it happened when I fitted the bulbar so this is expected...
Why do you think you should get more than 15mpg??
Best I have ever done is 17.3mpg on a looooong trip to Castleford last summer to get a wheelnut off....worst was 11mpg in the Isle of Wight greenlining!