I have just brought 96 disco 3.9i V8 with lpg conversion.

I have had a week and found that if i run it on petrol it does about 15-20 mpg but on lpg only does between 7-10 mpg i know that you lose a couple of mpg between the two but this is alot more than that.

I am sure that i read somewhere that i could adjust the mix by having someone sitting in the car and holding the revs at around 2000 rpm and slowly closing the valve until the revs started to drop then open by 1 1/2 turns.

Hi, I've never had an LPG V8i but my old 3.9 did 25MPG when REALLY careful or if you floored it everywhere it would go as low as 9 so your petrol comsumption is fine, but I read the LPG should be doing at least 17MPG so you are well low. Best bet is to look in the service book and find the LPG fitter who installed it, who should be LPGA registered, ring them and they maybe able to fax you a guide to adjust it or advise you what to do. Reason I say ask them is incase of warranty/insurance issues.

wouldnt play with the lpg personally, get it plugged in a reset, does it run strait in with the injectors or through the air flowmeter?