Hi Steve
Over all the miles I've driven on LPG, my V70 (an auto remember) always returned between 24 and 28 mpg.
What I found to be really important was changing the spark plugs every 10,000 miles. LPG is tough on plugs, and the best were without doubt the standard Denso single-point copper cored type. These also happened to be the cheapest too!
Multi-pin plugs won't be much use with LPG.
Other key things - keep an eye on the dissy, rotor and plug leads and change them at least every 100,000 miles, keep the LPG fuel filter changed at the specified interval (in my case every 15,000 miles), and don't use the air-con unless you really need to - it certainly does knock the mpg.
By way of comparison, my car returns between 28 and 32 mpg on petrol. On that basis I've been saving between 5p and 7p per mile in fuel costs. 240,000 LPG miles x 7p = £16,800 saved.
The original conversion cost was £1700, so I reckon I'm well ahead!
Cheers
Jack
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