LPG service should be annual at least..

LPG system do like the ignition system to be top notch for a good efficent urn, but aslong as the plugs are decent and clean, Iridiums are a waste IMHO....stick with decent NGK's half the price and just as good...leave Iridiums to the tuning boys in their Euro boxes...!!

9mpg is low even for around town...unless it is London/City traffic...a local town should be around 12-14 at least again IMHO.

Give me about a week and I'll let you know what mine is on the 4.6. Just had a new float sender fitted and put 82 litres of lpg in the tank. I'll see what I can get to.